Kurt Payne

Scan uploaded files with ClamAV or run system commands against uploaded files.  This allows you to integrate third party malware scanners.
This plugin requires either ClamAV or another third-party scanner to be installed.  This plugin will pass uploaded files to the scanner and take appropriate actions based ont he results, but it is not, itself, a malware scanner.
If you have a dedicated server, you can install <a href="http://php-clamav.sourceforge.net" rel="nofollow ugc">php-clamav</a> for performance and convenience.
Banner image from <a href="http://www.flickr.com/photos/runlevel0/3647554681/in/photostream/" rel="nofollow ugc">Eric Martinenz</a>

Upload Scanner

It may not have been updated in 4 years, but it's such a simple plugin that there's really no reason to... and it still works great with your server's ClamAV install.

Still does exactly what it claims

Scan all uploaded files with ClamAV or your favorite malware scanner

Vigilant – 100% Free Security Suite: Firewall, 2FA, Login, Headers, Scanner… vs Upload Scanner