Hackers defaced one of the Web sites of the Large Hadron Collider (LHC) earlier this week, but the controversial science project's network suffered no permanent damage, a spokesman for CERN maintained today.

The attack took place Monday, two days before the massive collider ran its first operational test, said James Gillies, a spokesman for the European Organization for Nuclear Research, or CERN, which operates the LHC.

A group going by the name Greek Security Team, or GST, claimed responsibility for the defacement of one of the LHC sites, cmsmon.cern.ch, according to a report earlier Friday in U.K. newspaper The Telegraph.

Hackers ended the long message that temporarily replaced the CERN site with the line: "We are 2600 - dont [sic] mess with us," the newspaper said.

It was a defacement, and that's all it was, said Gillies today. "It was benign, but it reminds us that we need to be vigilant," he said. "And no harm was done to the experiment or its computer network." No additional files, malicious or otherwise, had been injected into the project's computers, he said.

CERN brought the site back up but has blocked public access. Instead, only CERN users can reach the revived site.

The hackers targeted a site for the Compact Muon Solenoid (CMS), one of the major experiments being run at the LHC. Built around a huge solenoid magnet that generates a magnetic field 100,000 times more powerful than Earth's own, the CMS detector is designed to search for the Higgs boson particle and others that could make up the elusive dark matter scientists theorize comprises the bulk of the universe's matter.

The CMS detector is a rival of the ATLAS experiment, a second LHC sensor that uses radically different technologies and designs for its magnetic detector. CMS is located in France, while ATLAS is in Switzerland; the LHC sprawls across the Franco-Swiss border near Geneva.

Prior to Wednesday's test, some people had claimed that switching on the LHC would create a black hole that would destroy the earth. CERN responded last week with a report that dismissed the fears as "unfounded." Scientists associated with the project have also received death threats.

Site defacements are not unusual. Zone-H.org, a group that collects evidence of site attacks, logs hundreds each day. But attacks against internationally known domains are relatively rare. In June, for example, a Turkish hacker group broke into the site for the Phoenix Mars Lander, at the time a new NASA arrival on the Red Planet.