Mainz  - The number of web pages infected with viruses continues to climb.

Between January and March 2008, US-based IT security company Sophos discovered a newly-infected web site every five seconds on average.

A year ago, that figure stood at "just" every 14 seconds, the company reported from its Mainz offices. "Anyone who calls up infected web sites can count on attacks by malicious programs," explains Matthias Gaertner from the German Federal Agency for Security in Information Technology (BSI) in Bonn.

No matter what the content, cybercriminals attack specific security holes in web sites. Even reputable internet pages are not impervious to this.

"Hackers look very closely to see where they can cause the most damage. They undertake highly targeted surveillance of security holes on heavily trafficked web sites," the computer experts say. To protect against malicious software, Gaertner advises the use of both anti-virus software and a firewall. Regular application of security updates, known as patches, is also crucial. Even better protection is offered by programs that query users before allowing potentially dangerous Web sites to be called up.

The majority of infected web sites in the first quarter of 2008 were based in the US (42 per cent), followed by China (30.1 per cent) and Russia (10.3 per cent), the Sophos analysis found. Germany held fourth place with 2.2 per cent.

One major source of malicious software are games and expansion packs being traded on what are known as P2P networks, warns software maker G Data. A current study by the company found that of 1,000 files taken under the microscope, 65 per cent were virus infected. Six months ago that share lay at only 30 per cent. (dpa)