Since Saturday, thousands of Web pages have been defaced by hacking groups operating out of Morocco, Lebanon, Turkey, Iran, said Gary Warner, director of research in computer forensics with the University of Alabama at Birmingham.

The defacements have primarily affected small businesses and vanity Web pages hosted on Israel's .il Internet domain space. One such site, Rosh Ha’ayin, Israel's Galoz Electronics Ltd, whose hacked read "RitualistaS GrouP Hacked your System!!! The world isn't insurance!!! For a better world," on Wednesday.

Other attackers have placed more incendiary messages condemning the U.S. and Israel and adding graphic photographs of the violence. Warner said he has seen no evidence that any Israeli government site has been hit by these attacks, although they have been targeted.

On Saturday, Israel launched air strikes into Gaza in response to earlier rocket attacks from Hamas and other militant groups. The online attacks began soon after, Warner said. "It really got serious on Sunday," he said. "All the stops got pulled out."

Since then, Warner estimates that about 10,000 Web pages have been hacked. Many of these intrusions have been documented on sites such as which keeps track of hacked Web sites. Often these are mass defacements where many pages hosted on the same server are hit.