388. Ransomware Gang Abuses FTK Imager for Defense Evasion

Hello everyone!

Today we’ll talk about another forensic tool that attackers used in the context of the Impair Defenses technique: Disable or Modify Tools (T1562.001).

Once again, the topic is ransomware. This time, we’re looking at the STAC4713 cluster, which distributes the PayoutsKing ransomware. To add exclusions to Windows Defender, the attackers used FTK Imager - a forensic tool designed for creating disk images. The key point is that during installation, this tool allows a selected path to be added to exclusions, which is exactly what the attackers exploited.

The following command is executed:

powershell -command $ExclusionType;$ExclusionFile = '"ExterroExclusions.txt"';if(Test-Path -path $ExclusionFile ){ $Exclusions = Get-Content $ExclusionFile; foreach ($Item in $Exclusions ) { $ItemTrimmed = $Item.trim(); if($Item.length -gt 0){ if($ItemTrimmed.StartsWith('-')) { $ExclusionType = $ItemTrimmed; Write-Host $ExclusionType; } elseif ( !($ItemTrimmed.StartsWith('#'))) { if ($ExclusionType -eq '-Folder') { Add-MpPreference -ExclusionPath $ItemTrimmed; Write-Host "Adding "$ExclusionType" exclusion " $ItemTrimmed; } elseif ($ExclusionType -eq '-FileType') { Add-MpPreference -ExclusionExtension $ItemTrimmed; Write-Host "Adding "$ExclusionType" exclusion " $ItemTrimmed; } elseif ($ExclusionType -eq '-Process') { Add-MpPreference -ExclusionProcess $ItemTrimmed; Write-Host "Adding "$ExclusionType" exclusion " $ItemTrimmed; } } } }}else{ Write-Host "Did not find exclusion file " $ExclusionFile; Return;}

By the way, this isn’t the first time attackers have abused this tool. For example, according to this report, attackers installed FTK Imager on many hosts and used it not only to bypass security controls but also to access files containing credentials.

So, suspicious installation or execution events involving FTK Imager may indicate malicious activity on the network. It’s worth checking:

event_type: "processcreatewin"

AND

proc_file_productname: "ftk imager"

See you soon!

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