Russian cybercrime group FIN7, also known as Anunak and Carbanak, has been spotted exploiting a Veeam Backup & Replication vulnerability that was patched in March 2023. The group, which has been active since at least 2015, is primarily focused on stealing credit card information. It is believed that multiple sub-groups operate under the FIN7 umbrella, with some threat actors overlapping with ransomware groups such as REvil, DarkSide, BlackMatter, Alphv, and Black Basta.
Cybersecurity company WithSecure reported that in late March 2023, they detected FIN7 attacks exploiting internet-facing servers running Veeam Backup & Replication software to execute payloads on compromised environments. The firm observed a Veeam Backup process executing a shell command to download and execute a PowerShell script that turned out to be the Powertrash in-memory dropper, known to be used by FIN7. The dropper was employed to deploy Diceloader, a backdoor also known as Lizar, which allows attackers to perform various post-exploitation operations and has been linked to FIN7 in the past.
According to WithSecure, "The exact method used by the threat actor to invoke the initial shell commands remains unknown but was likely achieved through a recently patched Veeam Backup & Replication vulnerability, CVE-2023-27532, which can provide unauthenticated access to a Veeam Backup & Replication instance." CVE-2023-27532, which has a CVSS score of 7.5, was disclosed and patched in early March. Approximately two weeks later, proof-of-concept (PoC) exploitation code targeting the vulnerability was released publicly. Veeam claims that successful exploitation of the bug allows an attacker to obtain encrypted credentials stored in the configuration database, while penetration testing firm Horizon3.ai, which released the PoC, says that the flaw enables attackers to acquire cleartext credentials.
During the observed FIN7 attacks, WithSecure noted suspicious activity targeting the exploited Veeam backup instances several days before payloads were dropped, possibly to probe and identify vulnerable servers. The threat actor was seen conducting network reconnaissance, stealing information from the Veeam backup database, exfiltrating stored credentials, achieving persistence for the Diceloader backdoor, and moving laterally using the stolen credentials. WithSecure Intelligence identified two instances of such attacks conducted by FIN7, stating, "As the initial activity across both instances were initiated from the same public IP address on the same day, it is likely that these incidents were part of a larger campaign. However, given the probable rarity of Veeam backup servers with TCP port 9401 publicly exposed, we believe the scope of this attack is limited."
CVE-2023-27532 was addressed with the release of Veeam Backup & Replication versions 12 (build 126.96.36.1990 P20230223) and 11a (build 188.8.131.521 P20230227), which organizations need to install on the Veeam Backup & Replication server. Vulnerabilities in Veeam’s product have been exploited in previous attacks, and organizations are advised to update their Backup & Replication instances as soon as possible.