If your pen drive is affected by any virus/worm/malware then it is suggested to disable the autorun function in your computer.

Here are the steps to disable the autorun.

1.Go to start ->Run

Type gpedit.msc

press enter

2.In that go to Administrative Templates->System->Turn off autoplay

3.Now set it to Enabled if you want to turn off the autorun feature.

The default value will not configured

4.There is one more option in it

We have to select between All drives/ CD-ROM drives

Select CD-ROM drive if you want to disable autorun only for CDS or select all drives if you want to turn off autorun for all drives including your pen drives or flash drives