The "highly active" Gamaredon APT group has been using several previously undocumented post-compromise attack tools in malicious campaigns, which ESET researchers report have been increasing over the past few months. Many of these tools target Microsoft Office and Outlook.
Gamaredon has been active since at least 2013 and mostly targeted Ukrainian institutions, the research team reports in a new analysis, citing reports from CERT-UA and Ukrainian institutions. A recent increase in activity has brought "constant waves" of malicious emails with attachments packing malicious macros that, when executed, try to download different malware variants.
"The tools used by Gamaredon are very simple and are designed to gather sensitive information from compromised systems and to spread further," researchers say in a blog post. Even though its tools could download more subtle binaries, the group seems primarily focused on spreading far and fast in target networks. Unlike other APT groups, Gamaredon makes no effort to hide.
A closer look at post-compromise tools revealed a VBA macro targeting Microsoft Outlook that uses a victim's email account to send spear-phishing email to contacts in their Office address book. Using Outlook macros to send malware is rare in malicious campaigns, researchers note.
Their analysis also inspected variants of modules the Gamaredon group uses to inject malicious macros or remote templates into documents on the compromised system. This is an efficient way of moving throughout a network because employees commonly share files. And because macros are run when files are opened, it's a handy way to remain persistent as files are often opened several times. These modules are able to adjust Office macro security settings, researchers found, meaning a victim doesn't know they are compromised when they open malicious files.
Read the full report here.