T1091 Replication Through Removable Media

T1091 Replication Through Removable Media

High-Level Description

Adversaries may move onto systems, possibly those on disconnected or air-gapped networks, by copying malware to removable media and taking advantage of Autorun features when the media is inserted into a system and executes. In the case of Lateral Movement, this may occur through modification of executable files stored on removable media or by copying malware and renaming it to look like a legitimate file to trick users into executing it on a separate system. In the case of Initial Access, this may occur through manual manipulation of the media, modification of systems used to initially format the media, or modification to the media's firmware itself.

Mobile devices may also be used to infect PCs with malware if connected via USB. This infection may be achieved using devices (Android, iOS, etc.) and, in some instances, USB charging cables. For example, when a smartphone is connected to a system, it may appear to be mounted similar to a USB-connected disk drive. If malware that is compatible with the connected system is on the mobile device, the malware could infect the machine (especially if Autorun features are enabled).

Kill Chain Phase

• Lateral Movement (TA0008)
• Initial Access (TA0001)

Platforms: Windows

What to Check

• Identify if Replication Through Removable Media technique is applicable to target environment
• Check Windows systems for indicators of Replication Through Removable Media
• Verify mitigations are bypassed or absent (3 known mitigations)
• Assess detection coverage (1 detection strategies)

How to Test

Atomic Red Team Tests

The following tests are from Atomic Red Team and provide actionable ways to test this technique:

Atomic Test 1: USB Malware Spread Simulation

Simulates an adversary copying malware to all connected removable drives.

Supported Platforms: windows

$RemovableDrives=@()
$RemovableDrives = Get-WmiObject -Class Win32_LogicalDisk -filter "drivetype=2" | select-object -expandproperty DeviceID
ForEach ($Drive in $RemovableDrives)
{
write-host "Removable Drive Found:" $Drive