GeSWall 2.8 is a free intrusion prevention system (not an antivirus) that can protect your PC from anything without requiring daily updates (like a typical antivirus application). 
GeSWall prevents intentional or unintentional downloads from modifying your operating system in any damaging way, and by damaging I mean downloads that may:
- create registry entries
- modify registry entries
- create files
- modify files
- access confidential folders like My Documents
- log keystrokes
- inject code into processes
Per GeSWall’s website:
The generic rules for an isolated application are that the application:
1. Can read but cannot modify trusted resources.
2. Cannot read or modify confidential resources.
3. May create new untrusted resources, e.g. files.
4. May read or modify untrusted resources.
Check out my review of GeSWall here:
