Hom did not know why Childs is now refusing to divulge the passwords.

A source within DTIS, who spoke on condition of anonymity, painted a different picture of Childs. According to the source, just before his July 13 arrest, Childs intimidated the department's new chief of security, Jeana Pieralde, while she was conducting an audit of the network at San Francisco's data center. "He started to appear at a doorway and take a picture and walk away, clearly trying to intimidate her, watching her through the glass," the source said.

At one point he stood at the door and physically blocked her from exiting a room. "She went around the corner and locked herself into the office and called her boss," the source said. "At that point we knew he had something he was hiding."

Childs is being held on a US$5 million bond, an unusually high amount for a computer tampering case. He faces seven years in prison if convicted on all counts.

Childs' former public defender, who stepped down Thursday because of an unspecified conflict of interest, said that the $5 million bail is excessive. The DA's office has sought $1 million bonds in murder cases, said Mark Jacobs, an attorney with the San Francisco Office of the Public Defender. "I think they are trying to send a statement about how serious they take it," he said of the Childs case.

The city is now working with Cisco Systems to repair the problem, but if it has to replace the routers and switches that have been tampered with, it could easily face a US$250,000 bill for the incident.

San Francisco began rolling out the Fibre WAN about four years ago as a less-costly alternative to leased data lines. The city has spent more than $3 million on the project.