Research by Google has found that 10% of web sites contain malicious code designed to infect the visitor's PC and compromise their security.

A Research Paper released by Google shows the results of an anaylsis of several billion web addresses (URLs). An in-depth examination of around 4.5 million of these URLs revealed that around 450,000 were successfully launching malware code attacks, with an additional 700,000 that appeared malicious but were less successful.

The malicious sites, which made up 10% of all sites examined, contained code that attempted to automatically install software on the visitor's PC without their knowledge.

The owners of the web sites were often unaware that their sites were compromised, with hackers taking advantage of security vulnerabilities to hide malicious code in pages.

In some cases, sites that allow users to add content such as comments on blogs were compromised because they did not filter out potentially dangerous entries.

In other instances, malicious code was found in advertising provided by a third party.

Other methods of attack included enticing visitors to download infected files hidden as links to media content. For example, users may be told to download a special 'codec' to play certain video files, but in reality the codec is actually malware.

The study found that Trojans were by far the most common form of malware.

Web site users that become infected by malicious code are open to attack by hackers who can steal information, corrupt data and interfere with the working of the user's computer.

The research highlights the continued importance of protecting PCs from attack, by being cautious when clicking web or e-mail links, using security software such as anti-virus and firewall, and keeping Windows updated.

Related Tip: 5 Steps To Keep Your PC Safe Online