T1091 - Replication Through Removable Media

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.(Citation: Exploiting Smartphone USB ) This infection may be achieved using devices (Android, iOS, etc.) and, in some instances, USB charging cables.(Citation: Windows Malware Infecting Android)(Citation: iPhone Charging Cable Hack) 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).

Atomic Tests

Atomic Test #1 - USB Malware Spread SimulationSimulates an adversary copying malware to all connected removable drives.

Supported Platforms: windows#### Attack Commands: Run with powershell

$RemovableDrives=@()
$RemovableDrives = Get-WmiObject -Class Win32_LogicalDisk -filter "drivetype=2" | select-object -expandproperty DeviceID
ForEach ($Drive in $RemovableDrives)
{
write-host "Removable Drive Found:" $Drive
New-Item -Path $Drive/T1091Test1.txt -ItemType "file" -Force -Value "T1091 Test 1 has created this file to simulate malware spread to removable drives."
}

Invoke-AtomicTest T1091 -TestNumbers 1

Cleanup:

$RemovableDrives = Get-WmiObject -Class Win32_LogicalDisk -filter "drivetype=2" | select-object -expandproperty DeviceID
ForEach ($Drive in $RemovableDrives)
{
Remove-Item -Path $Drive\T1091Test1.txt -Force -ErrorAction Ignore
}

Invoke-AtomicTest T1091 -TestNumbers 1 -Cleanup

Detection

Monitor file access on removable media. Detect processes that execute from removable media after it is mounted or when initiated by a user. If a remote access tool is used in this manner to move laterally, then additional actions are likely to occur after execution, such as opening network connections for Command and Control and system and network information Discovery.

Shield Active Defense

System Activity Monitoring

Collect system activity logs which can reveal adversary activity.

Capturing system logs can show logins, user and system events, etc. Collecting this data and potentially sending it to a centralized location can help reveal the presence of an adversary and the actions they perform on a compromised system.

Opportunity

There is an opportunity to deploy a tripwire that triggers an alert when an adversary touches a network resource or uses a specific technique.

Use Case

A defender can monitor systems for the use of removeable media.

Procedures

Ensure that systems capture and retain common system level activity artifacts that might be produced. Monitor Windows systems for event codes that reflect an adversary changing passwords, adding accounts to groups, etc.