Sixty-five per cent of users have been infected by some kind of malware, according to corporate watchdog The CMO Council. Other recent studies suggest that as many as 80 per cent of personal computers connected to the net lack any form of security software.

Is the cost of security software putting you off? The good news is that it's entirely possible to successfully protect your machine with a well chosen combination of free software. Instead of opting for a paid security suite, you'll need to pick and choose the components of your 'suite' yourself, the programs may not update automatically, and you may not be entitled to free technical support. But you'll save a bundle of cash.

Build your security suite from these 10 free security apps for your Windows PC...

Free anti-virus

AVG Free is among the most popular anti-virus tools. There's a pay version for £29.99 which adds live monitoring of downloads, search results and instant messaging sessions. The free edition still has daily virus database updates, full system scanning capabilities and anti-spyware features.

Avast is another popular free anti-virus program while PC Tools offers PC Tools AntiVirus Free Edition. PC Tools also produces a product called ThreatFire, which helps to protect against Zero Day attacks, and works alongside any anti-virus apps.

Free spyware removal

Ad-Aware Free from Lavasoft can be used to bolster your machine's spyware resistance further, as can Spybot Search & Destroy.

Users of Windows XP can download Microsoft's Windows Defender. Windows Vista owners won't need to download it – it comes with the operating system.

Free firewall

You'd be hard-pressed to find a better free firewall than ZoneAlarm Free Firewall – from another company that also offers its own commercial security suite. An improvement over Windows built-in firewall, it's easy to configure and operate. PC Tools also offers a free Windows firewall.

Free spam protection

For spam protection download Mailwasher, which works with your local mail client such as Outlook. Alternatively, switch to a free online mail provider like Gmail or Hotmail.