Cisco Talos has uncovered an ongoing cyber marketing campaign by the Gamaredon menace actor group, focusing on Ukrainian customers with malicious LNK recordsdata to ship the Remcos backdoor.
Lively since no less than November 2024, this marketing campaign employs spear-phishing ways, leveraging themes associated to the Ukraine battle to lure victims into executing the malicious recordsdata.
The LNK recordsdata, disguised as Workplace paperwork, are distributed inside ZIP archives and carry filenames referencing troop actions and different war-related subjects in Russian or Ukrainian.
The assault begins with the execution of a PowerShell downloader embedded in the LNK file.
This downloader contacts geo-fenced servers situated in Russia and Germany to retrieve a second-stage ZIP payload containing the Remcos backdoor.
The downloaded payload employs DLL sideloading strategies to execute the backdoor, a way that entails loading malicious DLLs by way of official purposes. This strategy allows attackers to bypass conventional detection mechanisms.
Subtle Supply Mechanisms
Gamaredon’s phishing emails probably embody both direct attachments of the ZIP recordsdata or URLs redirecting victims to obtain them.
The marketing campaign’s filenames, similar to “Coordinates of enemy takeoffs for 8 days” or “Positions of the enemy west and southwest,” recommend a deliberate try to take advantage of delicate geopolitical themes.
Metadata evaluation signifies that solely two machines have been used to create these malicious shortcut recordsdata, in keeping with Gamaredon’s operational patterns noticed in earlier campaigns.
The PowerShell scripts embedded within the LNK recordsdata use obfuscation strategies, similar to leveraging the Get-Command cmdlet, to evade antivirus detection. As soon as executed, these scripts obtain and extract the ZIP payload into the %TEMP% folder.
The payload contains clear binaries that load malicious DLLs, which decrypt and execute the ultimate Remcos backdoor payload.
This backdoor is injected into Explorer.exe and communicates with command-and-control (C2) servers hosted on infrastructure based totally in Germany and Russia.
Focused Infrastructure and Indicators of Compromise
The marketing campaign’s C2 servers are hosted by Web Service Suppliers similar to GTHost and HyperHosting.
Notably, Gamaredon restricts entry to those servers based mostly on geographic location, limiting them to Ukrainian victims.
Reverse DNS data for a few of these servers reveal distinctive artifacts which have helped researchers establish further IP addresses related to this operation.
The Remcos backdoor itself offers attackers with strong capabilities for distant management, together with knowledge exfiltration and system manipulation.
Cisco Talos has noticed proof of unpolluted purposes like TivoDiag.exe being abused for DLL sideloading throughout this marketing campaign.
Gamaredon’s use of superior strategies similar to DLL sideloading, geo-fenced infrastructure, and thematic phishing underscores its persistence in focusing on Ukraine amidst ongoing geopolitical tensions.
Organizations are suggested to stay vigilant towards such threats by implementing strong endpoint safety, e-mail safety measures, and community monitoring options.
IOCs for this menace could be present in our GitHub repository right here.
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