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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.

ID: T1091
Tactic: Lateral Movement, Initial Access
Platform: Windows
System Requirements: Removable media allowed, Autorun enabled or vulnerability present that allows for code execution
Permissions Required: User
Data Sources: File monitoring, Data loss prevention
Version: 1.0

Procedure Examples

Name Description
Agent.btz Agent.btz drops itself onto removable media devices and creates an autorun.inf file with an instruction to run that file. When the device is inserted into another system, it opens autorun.inf and loads the malware. [9]
APT28 APT28 uses a tool to infect connected USB devices and transmit itself to air-gapped computers when the infected USB device is inserted. [4]
CHOPSTICK Part of APT28's operation involved using CHOPSTICK modules to copy itself to air-gapped machines and using files written to USB sticks to transfer data and command traffic. [3] [4]
Darkhotel Darkhotel's selective infector modifies executables stored on removable media as a method of spreading across computers. [15]
DustySky DustySky searches for removable media and duplicates itself onto it. [8]
Flame Flame contains modules to infect USB sticks and spread laterally to other Windows systems the stick is plugged into using Autorun functionality. [11]
H1N1 H1N1 has functionality to copy itself to removable media. [6]
njRAT njRAT can be configured to spread via removable drives. [12]
SHIPSHAPE APT30 may have used the SHIPSHAPE malware to move onto air-gapped networks. SHIPSHAPE targets removable drives to spread to other systems by modifying the drive to use Autorun to execute or by hiding legitimate document files and copying an executable to the folder with the same name as the legitimate document. [10]
Unknown Logger Unknown Logger is capable of spreading to USB devices. [7]
Ursnif Ursnif has copied itself to and infected removable drives for propagation. [13] [14]
USBStealer USBStealer drops itself onto removable media and relies on Autorun to execute the malicious file when a user opens the removable media on another system. [5]

Mitigations

Mitigation Description
Disable or Remove Feature or Program Disable Autorun if it is unnecessary. Disallow or restrict removable media at an organizational policy level if it is not required for business operations. [1] [2]
Limit Hardware Installation Limit the use of USB devices and removable media within a network.

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.

References