PITTSBURGH - The University of Pittsburgh endured another series of bomb threats Thursday, as other schools in and around the city began receiving the so-far baseless and anonymous threats for the first time.
The Western Pennsylvania School for the Blind in Pittsburgh received a threat Thursday. Point Park University, California University of Pennsylvania and the Community College of Allegheny County all received bomb threats in the last week.
Authorities aren't releasing any more details about who is behind the rash of threats, though they said Wednesday that they've made significant progress in the investigation.
Police arrested one man Wednesday for separate threats against Pitt professors, but the spate of bomb threats continued even after the man was in custody.
The first threats were scrawled on restroom walls, but more recently they have been sent by email to the school or to local newspaper reporters. Authorities said some of the threats have been traced to or through computers in Austria, but nobody has been charged with making them.
One expert on computer security said the anonymous email program that was reportedly used to deliver some threats is very hard to trace.
Lorrie Cranor is director of the CyLab Usable Privacy and Security Laboratory at Carnegie Mellon.
"Anonymous tools are a double-edged sword," Cranor said, referring to the MixMaster email program. The program essentially strips background data about the sending computer from the message and then bounces the message through various computer servers - sometimes in different countries - to further obscure the origin.