But there are no such a good, free USB antivirus is available, you need to pay to get a good one. Trustport Antivirus USB/U3 Edition is one of the best in this category and under a promotion you can get a full functional USB Antivirus free for 6 months.
Trustport Antivirus USB edition prevents malicious codes to be copied onto the flash disk, enables scanning of the host computer. It allows encryption of files to prevent unauthorized access; it brings reliable shredding of unused private data. It doesn’t require hard drive installation.
Just follow this link and fill-up the form (you should give other three email addresses of your family members) and submit to get your license key.