The FBI on Thursday published indicators of compromise (IOCs) associated with the continuous exploitation of Fortinet FortiOS vulnerabilities in attacks targeting commercial, government, and technology services networks.
In early April, the FBI along with the Cybersecurity and Infrastructure Security Agency (CISA) warned that threat actors had been targeting serious security holes in Fortinet’s flagship operating system FortiOS for initial access into victims’ networks.
The targeted bugs include CVE-2018-13379 (a path traversal in the FortiOS SSL VPN web portal), CVE-2020-12812 (a bypass of FortiOS SSL VPN two-factor authentication), and CVE-2019-5591 (default configurations ship without LDAP server identity verification).
While initial activity only involved scanning for devices vulnerable to the FortiOS SSL VPN web portal flaw (on ports 4443, 8443, and 10443), as well as enumeration of devices potentially impacted by the other two bugs, the attackers have since moved to network compromise and additional malicious activity.
“As of at least May 2021, an APT actor group almost certainly exploited a Fortigate appliance to access a webserver hosting the domain for a U.S. municipal government. The APT actors likely created an account with the username ‘elie’ to further enable malicious activity on the network,” the FBI now says.
The agency says that another account likely associated with this activity is “WADGUtilityAccount,” which, similar to “elie,” threat actors might have established on active directories, domain controllers, servers, and workstations. Network administrators should also look for other unrecognized accounts.
Additionally, admins should be wary of executable files such as Audio.exe (or frpc.exe) and Frps.exe, of outbound FTP traffic on port 443, a scheduled task named “SynchronizeTimeZone,” and the use of tools such as Mimikatz, MinerGate, WinPEAS, SharpWMI, BitLocker, WinRARwhere, and FileZilla. Some of these might be benign, unless used when unexpected, the FBI notes.
Administrators are also advised to take all the necessary measures to ensure the security of networks, including keeping systems patched and continuously updated, implementing network segmentation and multi-factor authentication, applying the principle of least privilege, keeping data backed up, employing malware detection tools, and periodically checking the environment for suspicious activity.