Untangle is open source and offers a free version. The free version provides the following:
- Web URL filter
- Virus Scanner & Blocker
- Spam Blocker
- Attack Blocker
- Phish Blocker
- Spyware Blocker
- Protocol Control (Layer-7 filtering)
- Captive Portal
- Intrusion Prevention
It currently does not provide a caching proxy, but I received an email notification today that the Untangle Web Cache feature request ticket, that was opened 2 years ago, has been assigned to a developer and should be included in Untangle 8.1. The current version as of this writing is 8.0.
I don't know when it's due, but that's certainly great news! I've been told by many people that making squid work with clamav is a huge headache as it often just dies (squid). So I'm guessing the Untangle team has finally worked a way to get around these issues.