This guide describes how you can automatically scan files uploaded by users through a web form on your server using PHP and ClamAV on Debian Etch or Ubuntu
Read it at howtoforge
That way you can make sure that your upload form will not be abused to distribute malware. To glue PHP and ClamAV, we install the package php5-clamavlib/php4-clamavlib which is rather undocumented at this time. That package is available for Debian Etch and Sid and also for Ubuntu Dapper Drake and Edgy Eft, so make sure you use one of these platforms.