One out of every eight computer attacks is being made via USB devices targeting the Windows AutoRun function, according to security software firm Avast.
Avast said it has detected a growing number of malware attacks targeting the AutoRun function in Windows and plug-in USB devices. Of the 700,000 recorded attacks on computers across the avast user community during the last week of October, one out of every eight attacks - or 12.5 percent - came via USB devices.
Avast said the "key attack point" for the malware is the AutoRun feature in Windows. AutoRun alerts computer users when a new device such as a memory stick is connected, and is designed to help them choose what application should run with the new files.
"AutoRun is a really useful tool, but it is also a way to spread more than two-thirds of current malware. The threat of USB-distributed malware is much more widespread than just the Stuxnet attacks on enterprise computers - which were also spread via infected memory sticks," said avast virus analyst Jan Sirmer.
"Cyber-criminals are taking advantage of people's natural inclination to share with their friends and the growing memory capacity of USB devices. Put these two factors together and we have an interesting scenario."
Avast said AutoRun is misused when a USB device infected by "INF:AutoRun-gen2 [Wrm]", avast's generic detection term for this type of malware worm, is connected to a computer.
The infected device - which could also be a PSP, digital camera, a mobile phone or an mp3 player - starts an executable file which then invites a wide array of malware into the computer. The incoming malware copies itself into the core of the Windows OS and can replicate itself each time the computer is started.
Avast's USB safety pointers:
-Be aware. Around 60 percent of malware can now be spread via USB devices
-Don't start attached. Turning on a PC with a USB device attached can result in malware being loaded directly to the computer ahead of some antivirus programs starting up
-Scan first, look second. Make sure you have enabled "on-access auto-scans" in your antivirus program