By SHARON TERLEP
DETROIT—General Motors Co. officials were red-faced on Wednesday after software on a network at its headquarters was programmed to insert a derogatory remark on computer browsers after any mention of Chrysler Group LLC and several other competitors.
The prank came to light at GM's unveiling of a battery-powered version of its Chevrolet Spark small car at a five-day event marking the 100th anniversary of GM's Chevrolet brand. The event drew more than 200 journalists from around the world.
Selim Bingol, a GM spokesman, said the auto maker had nothing to do with the prank. GM has since corrected the problem.
GM officials said computer technicians found an unauthorized software program had been installed on a wireless router, and the program was altering the way Web pages were displayed to insert the word "sucks" after any mention of certain rivals on computers linked to the network.
Later in the day, GM said it had identified the culprit—a subcontractor who had helped set up the wireless network. GM didn't identify the company but said the subcontractor had admitted its role and intended the prank to be humorous.
"These guys are learning the definition of sucks," Mr. Bingol said.
Computers accessing the Internet via other networks at the company's headquarters were unaffected.
The word "sucks" appeared after mentions of Chrysler, Ford Motor Co., Toyota Motor Corp., and Honda Motor Co. on any searches or references to those companies conducted on computers using the GM network. Web references were not permanently altered because the word was inserted only onto the displays of computers using that one network.
The word did not appear after mentions of Nissan Motor Co., Hyundai Motor Co., or Volkswagen AG.