Date: 4 February 2020
An Alert is used to raise awareness of a recently identified cyber threat that may impact cyber information assets, and to provide additional detection and mitigation advice to recipients. The Canadian Centre for Cyber Security ("Cyber Centre") is also available to provide additional assistance regarding the content of this Alert to recipients as requested.
The Cybersecurity and Infrastructure Security Agency (CISA) has produced an Alert regarding their ongoing investigation of the Citrix CVE-2019-19781 vulnerability. The Cyber Centre would like to highlight this Alert as it provides valuable information to system owners and operators responsible for defending their systems and networks from cyber threats. The Cyber Centre previously reported on these vulnerabilities over the past several weeks (see references); the CISA report contains additional detailed information.
The CISA Alert can be found at:
Should activity matching the content of this Alert be discovered, recipients are encouraged to contact the Cyber Centre by email (firstname.lastname@example.org) or by telephone (1-833-CYBER-88 or 1-833-292-3788).
Due to the severity of CVE-2019-19781 and the ease by which threat actors are currently able to access working code to compromise unpatched and unmitigated Citrix devices, the Cyber Centre advises organizations that have not yet applied mitigations or patches to assume that they have already been compromised. The Cyber Centre strongly advises system owners who have not yet applied patches or mitigations to immediately disconnect their Citrix appliance(s) from the Internet and begin a full forensic investigation. Please note that recently applied mitigations or patches will not negate an active compromise that may have occurred while the appliance was in a vulnerable state. The indicators of compromise and tools for detecting compromise provided by Citrix, the Cyber Centre, CISA and other security researchers are not exhaustive, and should be used as a starting point for a full forensic assessment.
INDICATORS OF COMPROMISE
Below are IOC’s reported in Open Source that have not yet been highlighted in Cyber Centre reporting:
Backdoor (Written in GO)
Citrix Security Advisory (AV19-291):
Active Exploitation of Citrix Vulnerabilities (AL20-003):
Citrix Security Advisory (AV20-016):
Citrix Security Advisory (AV20-020):
TrustedSec NetScaler Honeypot:
Citrix - Indicator of Compromise Scanner (CVE-2019-19781)
NOTE TO READERS
The Canadian Centre for Cyber Security (Cyber Centre) operates as part of the Communications Security Establishment. We are Canada's national authority on cyber security and we lead the government's response to cyber security events. As Canada's national computer security incident response team, the Cyber Centre works in close collaboration with government departments, critical infrastructure, Canadian businesses and international partners to prepare for, respond to, mitigate, and recover from cyber events. We do this by providing authoritative advice and support, and coordinating information sharing and incident response. The Cyber Centre is outward-facing, welcoming partnerships that help build a stronger, more resilient cyber space in Canada.