DansGuardian Anti-Virus Plugin
Our software is a GPL addon that takes the Virus Scanning capabilities of The MailScanner and integrates them into the content filtering web proxy DansGuardian. We will eventually have a Source Forge project.
Currently all content is scanned for viruses (except SSL traffic). In the future, you will be able to disable the scanning and will be able to specify certain mime-types and/or file extensions that shouldn't be scanned (though I think this is a bigger security risk than just losing a couple of seconds of time waiting for the file).
The files/pages will appear to not be being downloaded. This is due to the fact that all the content/file has to be downloaded by the proxy before it can be scanned. I have implemented a trickle effect, where if you are downloading a file and it takes longer than 30 seconds, you get the first byte of the file. After that it only trickles a byte every minute. This has proven to keep the browser alive. The only potential drawback is if the file is infected, the user possibly has the first couple of bytes of the infected file.
Currently F-Prot is the only anti-virus engine tested. See MailScanner for a complete list of supported virus engines. I have tried converting the parsing code for the other engines, but since I don't have access to them, I can't test the code.
Sophos has been confirmed as working by a tester.
2002-08-14 - 1.0rc2 released. Adds ability to disable the virus scanning code completely and all file streams (non html/text) are written to disk immediately instead of being kept in memory. This provides for much faster performance.