The stealthy and perniciously quick computer worm that infiltrated corporations and crashed personal computers around the globe also hit the Maryland Motor Vehicle Administration yesterday, forcing officials to close all 24 offices and inconveniencing thousands of drivers.

The worm, called Blaster, also contaminated most computers in Montgomery County government departments, except for police, fire and emergency services, said Donna Bigler, a county spokeswoman. The county's network was back up by 2 p.m.

Jack Cahalan, a MVA spokesman, said the trouble in the state's system was detected in the morning after many of the agency's computers wouldn't work. By noon, all the offices were closed and teams of technicians had fanned out across the state to fix the 1,700 computers so that business would be able to return to normal by 8:30 this morning.

Driver's licenses and vehicle registrations that expired yesterday will get a one-day extension, Cahalan said. Customers can also call 1-800-950-1MVA to make sure the offices are open.

"Our people will work into, if not through, the night to make sure" the offices are open, said David Hugel, chief deputy administrator of the MVA.

That was little solace to the steady stream of frustrated customers who arrived at MVA stations across the state yesterday only to find them shuttered and dark.

When Chris Snipes, 31, drove into the near-empty parking lot at the Annapolis office, he thought, "Oh, great! No line." But when he learned that the office was closed, his spirits dropped. It had taken him 30 minutes to get there from his home in Lothian. And now, he said, he'd have another half-hour ride back. "For nothing," he added.

Many who showed up at MVA offices yesterday said that beyond the inconvenience, there was a deeper worry that the agency's computer network, which handles an average of 54,000 transactions a day, could be so quickly hobbled. They feared that sensitive information could leak out and that the government should be better prepared to handle attacks on its systems.

"They have my date of birth, my address in there -- all the stuff people could steal your identity with," said Theresa Hommel, 61, who had wanted to renew her handicapped-parking sticker.

Cahalan said that customers shouldn't worry because the worm did not affect MVA's mainframe. "The data is secure and untouched," he said.

He said there was nothing more the MVA could do to defend its network from the fast-moving worm that hit more than a million computers worldwide. It also crashed the computer network at the U.S. Court of Federal Claims in the District, sending some employees home.

Worms are malicious programs designed to infect, harm and disable computers. They spread through internal networks and the Internet and do not require people to open e-mail attachments or take other actions in order to function. Yesterday's worm is also known as LoveSan and MSBlaster.

"There are a wide variety of safeguards in the software system at MVA," Cahalan said. "What we're dealing with today obviously is a sophisticated virus that has penetrated many of the most secure sites across the country."

"Our goal is to do everything humanly possible to prevent a virus from getting into the system or to take aggressive steps, as we did today, to prevent it from spreading," he said.

Henry Fawell, a spokesman for Gov. Robert L. Ehrlich Jr. (R), said no other state agencies were affected, "but we're keeping our ears to the ground." He added that MVA's problem was the worst computer contamination the state has experienced.

In Montgomery, the worm infiltrated the county's network, even requiring librarians to check materials out manually, but caused no permanent damage, Bigler said.

"It gave people a chance to clean out their files," she said.

James Barnes, owner of Barnes and Sons Construction Co. in Waldorf, didn't have such a positive attitude when he realized that he wouldn't be able to get new license plates at MVA's Largo office.

"I feel like I came all the way up here for nothing," he said. "Now I have to take another day off from work to take care of this."

Michael Harding, 19, who had wanted to get a title for his car yesterday, will have to make another lunch-hour trip from the Home Depot in Bowie, where he works, to the Annapolis office.

"It's an inconvenience," he said shortly after seeing the sign on the door that read: "Hopefully Re-Open Wednesday."

Brian Krebs of washingtonpost.com contributed to this report.