The controversy over a Danish newspaper's publication of cartoons depicting the prophet Mohammed is being felt on the internet, where hackers have struck down and defaced hundreds of Danish websites in the past week, according to a website that tracks digital attacks.

Approximately 800 Danish websites have been hacked since the end of January, when reaction to the cartoons began to receive widespread media attention, said Roberto Preatoni, founder of the website.

On yesterday, about 200 Danish sites were reported as hacked with many of them being defaced with messages "in support of this Islamic war on the internet," Preatoni said. Typically between five and 10 Danish sites are reported hacked each day, he said.

Messages on the hacked sites include "don't ever tallk [sic] about our prophet," "[expletive] Denmark," and "Let the Muslim people live in peace [expletive]."

Most of the hackers are "posting hate messages", Preatoni said, but there are exceptions. "In some examples, we actually saw intelligent educated people who hacked and posted very polite messages, explaining what they were thinking."

The 12 cartoons, originally published on 30 September by the Danish newspaper Jyllands-Posten have offended Muslims the world over and sparked attacks by protesters on Danish embassies in Tehran, Beirut, and Damascus.

Preatoni estimates that another 700 non-Danish sites have also been hacked in connection with the cartoons.

The website contains about 10 years' worth of data on hacked sites, most of it submitted by the hackers themselves, including information on the motivation behind the attacks.

Other worldwide hacking protests have flared up in the past, including a surge in attacks after a US spy plane was downed in China in 2001. After the 2003 US-led invasion of Iraq, there was also a "massive Islamic protest" on the internet, Preatoni said.

The reaction to the Danish cartoons, however, has yielded the largest number of defacements in such a short time, according to Preatoni. "Islamic hackers, regardless of where they are located in the globe, they are uniting in this general protest against Denmark," he said.

One Danish site that has apparently not been defaced is that of the Jyllands-Posten itself. It has been the target of a number of DoS (denial of service) attacks, where attackers attempt to flood the site with so many requests that it ceases to operate, but it has remained in operation, said Mikko Hypponen, director of antivirus research with F-Secure. "Outside of that, I'm not aware of any hack attacks that have succeeded in any way," he said. "It has not been defaced."