The problem with traditional anti-virus (or any security) tools is that they rely on you to auto-update the definition database to combat the latest threats. Without an updated database, you could quite easily open an email attachment and suffer from an infection, without any detection from your security software.

Pro-active tools such as PC Tools ThreatFire attempt to combat this by trying to notice particular traits that a Trojan will use to infect your machine and then intercept or at least warn you that a process is performing erratically. Problem with this approach is that, if the latest Trojan finds a new way of infecting your machine, even the pro-active tools may not correctly understand the threat.

One alternative solution is Trend Micro’s HouseCall which is an online tool which you can use to scan your computer for the latest threats. However, as it’s online, they can keep their definitions bang up-to-date. Clearly the downside is that you have to manually run the checker, so it’s not going to perform any kind of automatic pro-active prevention when you open an infected file – it’s only good for scanning your system to check for potential problems.

Note that this is the beta preview of HouseCall 7 which is now Windows 7 compatible.