Many people think that installing anti-virus, firewall and anti-spyware software should inoculate them from all manner of threats. While it’s true that a decent security package or collection of security tools is necessary to help protect your PC from infection (click here for a list of useful tools if you haven’t yet secured your PC at all), in truth you need to be a bit more savvy than that.

Read on to find out 10 ways to close the security holes that still remain on your PC.

1. Augment your anti-virus tool

Threatfire is designed to work alongside existing security products. Unlike traditional anti-virus tools, it doesn’t rely on signatures to identify malware; instead, it monitors your PC for suspicious malware-like behaviour. The only time you’ll hear from the program is when it’s found something suspicious; otherwise it’ll sit silently in the background.

2. Vet your email

Most anti-spam tools only process email that’s been downloaded from your mail server – install POP Peeper and it’ll tell you when new mail has arrived at your mail server, ready for downloading. More importantly, you can preview your mail while it’s still on the server, deleting unwanted and suspicious messages without exposing them to your mail program.

3. Don’t click mail links

Never visit web sites by clicking links in your email unless you’re 100 per cent sure the link is safe. This is especially true for emails purporting to come from financial institutions asking you to log in to verify your account details – 99.9% are scams (the other 0.1% are irresponsible).

4. Switch to plain text

HTML can be used to hide all sorts of unpleasant things in email. Set your mail program to view all messages as plain text by default – you should see an option for viewing individual messages as HTML when you trust the sender.

5. Switch web browser

Upgrade to the latest version of Internet Explorer (use Windows Update) or switch to a browser that doesn’t support potentially malicious Active-X controls such as Firefox, Opera or Google Chrome. Check the browser’s privacy and security settings are set to Medium High or greater.

6. Check web sites before you visit

Some security packages – including Norton Internet Security and Kaspersky Internet Security – now provide browser add-ons that rate each site you visit using traffic light icons to alert you to dangerous and untrustworthy sites.

If your security package doesn’t offer this functionality, or you want a second opinion, install the free Web of Trust (WOT) plug-in for your browser – separate plugins are available for Internet Explorer, Firefox and Chrome – and you’ll be in a better position to avoid unsafe web sites thanks to its traffic-light system for both sites and search engine results.

7. Screen all downloads

Never open attachments or downloads directly – save the file to your hard drive, right-click it and run a quick scan with your security tool of choice prior to opening it if it’s not scanned automatically on downloading. Also make sure you download from a reputable web site (typically the program’s own home page or a respected download site like DownloadCrew) – the WOT plug-in will help here.

8. Manage your passwords

A password manager such as LastPass enables you to securely and easily enter your login details for all your websites – it works across multiple browsers and computers, so all you need to remember is your master password and email address. With this there’s no excuse to use the same password across all your online accounts – the program will even generate secure, random passwords for you.

If you’d like to extend this functionality to any program on your PC, try KeePass or KeePass Portable instead.

9. P2P basics

Peer-to-peer networks are a breeding ground for malicious software, particularly in content that’s been copyrighted. If you can’t live without P2P, pick a trusted provider and client such as uTorrent. Be careful what you share, and scan all downloads prior to opening them.

10. Create a sandbox

One way to beat viruses at their own game is to run your computer in a virtual environment, which is completely isolated from the real world. That way, any malware infections are trapped in the virtual world, eliminated when you restart your PC.

There are a number of programs out there which can provide this kind of functionality – one such tool that’s free for personal use is Returnil System Safe 2011 Home Free. This basically runs Windows in a virtual environment – all changes to your PC, including malware infections, are lost the moment you restart your PC. It’s also a great environment for testing out unknown applications, but you’ll have to upgrade to the Pro version if you want to be able to save files from your virtual environment back to your real one.