The Cybersecurity and Infrastructure Security Agency (CISA) and the Federal Bureau of Investigation (FBI) have released a joint cybersecurity advisory regarding advanced persistent threat (APT) actors chaining vulnerabilities — a commonly used tactic exploiting multiple vulnerabilities in the course of a single intrusion — in an attempt to compromise federal and state, local, tribal, and territorial (SLTT) government networks, critical infrastructure, and elections organizations.

CISA has recently observed advanced persistent threat (APT) actors exploiting multiple legacy vulnerabilities in combination with a newer privilege escalation vulnerability — CVE-2020-1472 — in Windows Netlogon. The commonly used tactic, known as vulnerability chaining, exploits multiple vulnerabilities in the course of a single intrusion to compromise a network or application. 

This recent malicious activity has often, but not exclusively, been directed at federal and state, local, tribal, and territorial (SLTT) government networks. Although it does not appear these targets are being selected because of their proximity to elections information, there may be some risk to elections information housed on government networks.

CISA is aware of some instances where this activity resulted in unauthorized access to elections support systems; however, CISA has no evidence to date that integrity of elections data has been compromised. There are steps that election officials, their supporting SLTT IT staff, and vendors can take to help defend against this malicious cyber activity.

Some common tactics, techniques, and procedures used by APT actors include leveraging legacy network access and virtual private network (VPN) vulnerabilities in association with the recent critical CVE-2020-1472 Netlogon vulnerability. CISA is aware of multiple cases where the Fortinet FortiOS Secure Socket Layer (SSL) VPN vulnerability CVE-2018-13379 has been exploited to gain access to networks. To a lesser extent, CISA has also observed threat actors exploiting the MobileIron vulnerability CVE-2020-15505. While these exploits have been observed recently, this activity is ongoing and still unfolding.

After gaining initial access, the actors exploit CVE-2020-1472 to compromise all Active Directory (AD) identity services. Actors have then been observed using legitimate remote access tools, such as VPN and Remote Desktop Protocol (RDP), to access the environment with the compromised credentials. Observed activity targets multiple sectors, and is not limited to SLTT entities.

CISA recommends network staff and administrators review internet-facing infrastructure for these and similar vulnerabilities that have or could be exploited to a similar effect, including Juniper CVE-2020-1631, Pulse Secure CVE-2019-11510,  Citrix NetScaler CVE-2019-19781, and Palo Alto Networks CVE-2020-2021 (this list is not considered exhaustive).