By far, the greatest security precaution you can take is to keep your operating system current. Microsoft has teams of extremely clever engineers working around the clock to find new vulnerabilities and correct them. These corrections are usually in the form of operating system patches. These patches can correct a wide range of problems or simply change the permission of a single file. Regardless of the extent of each patch, the need to update your operating system is crucial, so check for patches regularly.
OK, now that your operating system is updated, take a moment to check your anti-virus signature database. The signature database is used to identify all known exploits. Without a recently updated signature database, your anti-virus software can become very useless very quickly, so take another moment to check for updates to your anti-virus system.
When a new virus or exploit is discovered, there is a critical period of time after a patch is published but before you have updated your environment. During this time, very clever hackers are likely to disassemble the patch to discover the effect it will have on the target system. This discovery will lead to the cause of the underlying vulnerabilities, which can lead to newly crafted exploits guaranteed to work on systems that do not have the most recent patch. It doesn’t take long for new exploits to proliferate in this environment, so keeping an up-to-date operating system is more important than ever.