Antivirus software, firewall, and automatic updates are all available through the Windows Security Center, which is accessible from Start | Control Panel | Security Center. Check to ensure they are all enabled.
These three defences are technical, and compliance is easy. Once they’re set up, the computer does the work for you. Criminals know that these three methods provide protection to your computer. Instead, they work on the next weak link of the chain: YOU.
Malware looks for computers it can connect with for file shares, printer shares, logging on, etc. Once it finds one, it tries brute force password checking. This goes on in the background (users are not aware that this is going on), and tens of thousands of guesses can be made each hour. These brute force attempts work from a 100,000 word dictionary and they will try words forwards, backwards, with numbers appended to them, etc… It is essential that you have a well-chosen password.
A newer, more state-of-the-art method is to use a pass-phrase on systems which allow them. Many systems allow for 40-100 character passwords. A full sentence is more secure and easier to remember than a shorter, complicated password.
Finally, criminals will try to trick you into running something, and there are many ways this can be done. There is a constant barrage of spam/email enticing you to visit a website, which will have you downloading software. P2P software is also a great source of unwanted downloads. Be suspicious of anything you receive. Don’t run things from unknown websites. Don’t provide information to emails requesting it. Show criminals that you’re smarter than they are.