avast! U3 Edition's a mobile version of Avast anti-virus, that is designed to protect U3 smart drives from viruses and other forms of malware. The program can also be used to scan files or folders on the host computer that is connected to your USB drive. You can create a list of trusted computers, and automatically scan all other machines for virus infections as soon as you insert your USB drive, thereby preventing any host infection to spread to your USB drive. Other features include automatic virus signature updates, real-time virus shield and proxy support.

The license of this software is Free Trial Software, the price is $19.95, you can free download and get a free trial.