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).
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.
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.
|M1040||Behavior Prevention on Endpoint||
On Windows 10, enable Attack Surface Reduction (ASR) rules to block unsigned/untrusted executable files (such as .exe, .dll, or .scr) from running from USB removable drives. 
|M1042||Disable or Remove Feature or Program|
|M1034||Limit Hardware Installation||
Limit the use of USB devices and removable media within a network.
|ID||Data Source||Data Component||Detects|
Monitor for newly constructed drive letters or mount points to removable media
Monitor for unexpected files accessed on removable media.
Monitor for newly constructed files on removable media
Monitor for newly executed 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.