US-CERT is aware of public reports of an increase in malicious code propagating via USB flash drive devices. Currently, there are two popular methods by which USB flash drives are being infected with malicious code. Please note that these are not the only two methods available.

The first of these methods is referred to as simple file copy. This means that the malicious code initially resides on an infected computer and copies itself to all the storage devices connected to the affected computer. This method requires the user to access the USB flash drive and execute the malicious code.

The second method is referred to as AutoRun.inf modification. This means that the malicious code alters or creates an autorun.inf file on targeted storage devices connected to the affected computer. When an infected USB flash drive is connected to another computer, the malicious code can be automatically executed with no additional user interaction.

US-CERT encourages users to do the following to help mitigate the risks:

• Install antivirus software and keep the virus signatures up to date.
• Do not connect an unknown or untrusted USB drive to your computer.
• Disable AutoRun or AutoPlay features for removable media.
• Review the Using Caution with USB Drives Cyber Security Tip for more information on protecting your USB flash drive.
• Review The Dangers of Windows AutoRun Vulnerability Analysis Blog entry for more information regarding AutoRun.