Attackers used publicly available penetration testing and exploitation tools, the FiveHands ransomware, and the SombRAT remote access Trojan to steal information, obfuscate files, and demand ransom, officials report. They also used publicly available tools for network discovery and credential access.
The initial access vector in these attacks was a zero-day vulnerability in a virtual private network (VPN). In its recommendations to organizations, the CISA advises using multifactor authentication, particularly on all VPN connections, external-facing services, and privileged accounts. It also advises decommissioning unused VPN servers, which could be an entry point.
Analysis of the FiveHands ransomware is still ongoing; CISA plans to update its report as new information becomes available.