By Flavio Costa, Chris Neal and Guilherme Venere. In a recent customer engagement, we observed a month-long AvosLocker campaign. The attackers utilized several different tools, including Cobalt Strike, Sliver and multiple commercial network scanners. The initial ingress point in this incident was a pair of VMWare Horizon Unified Access Gateways that were vulnerable to Log4Shell. While Cisco products were deployed on the network, the appliances were never configured, allowing the attacker to gain access to internal servers and maintain a foothold. During the time the attacker was active in the network, several security events were detected by the security products but were not reviewed by the security team, which could have prevented the ransomware activity.
Threat Actor Profile: Avos
Avos is a ransomware group first identified in 2021 initially targeting Windows machines. More recently, a new ransomware variant of AvosLocker, named after the group, is also targeting Linux environments. Well-funded and financially motivated, Avos has been active since June 2021 and follows the ransomware-as-a-service (RaaS) model, an affiliate program to recruit potential partners. The announcement of the program includes information about the features of the ransomware and lets affiliates know