What is it?
Inf/autorun is a class of threats that exploit the insecure implementation of autorun on most Windows computers.
How does it work?
When removable media is attached to a computer, Windows will automatically try to run a program.
Should I be worried?
The bad guys use autorun to automatically install malicious software without the user doing anything more than plugging something into the computer or inserting a CD or DVD.
How can I prevent it
Nearly one out of 10 pieces of malware use autorun to help them spread. If you have autorun enabled on your computer, then you are at risk, even when you purchase a brand new USB device. The best protection against this threat is to disable autorun and use anti-virus software that you keep up-to-date. In the coming months, Microsoft will provide a patch to dramatically decrease the risk of autorun, but for more than 10 years, autorun has been Microsoft's worst known unpatched vulnerability.
