March 22, 2023

Atom Silo, a newly spotted ransomware group, is targeting a recently patched and actively exploited Confluence Server and Data Center vulnerability to deploy their ransomware payloads.

Last month,Atlassian issued security updates to patch a Confluence remote code execution (RCE) vulnerability tracked as CVE-2021-26084 and exploited in the wild. This will lead to sucessful command execution.

Atom Silo operators use “several novel techniques that made it extremely difficult to investigate, including the side-loading of malicious dynamic-link libraries tailored to disrupt endpoint protection software.”

After compromising Confluence servers and installing a backdoor, the threat actors drop a second-stage stealthier backdoor using DLL side-loading to launch it on the breached system. Ransomware payloads deployed by Atom Silo also come with a malicious kernel driver used to disrupt endpoint protection solutions and evade detection.

Atom Silo made significant efforts to evade detection prior to launching the ransomware, which included well-worn techniques used in new ways. Other than the backdoors themselves, the attackers used only native Windows tools and resources to move within the network until they deployed the ransomware.

Although these attackers were only deploying cryptocurrency miners, they could quickly escalate to ransomware payloads and data exfiltration once the threat actors started moving laterally through corporate networks from hacked on-prem Confluence servers. If internet facing servers have an unpatched security vulnerability.. how hazardous it is this incident shows.

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