PHILADELPHIA -- We have all been bothered by those pop-up advertisements while trying to search the Internet. Recently those annoying ads also plagued the Philadelphia Police Department.

There have been computers on board police patrol cars for a number of years. They are called MDTs, or mobile data terminals. They are now as much of a part of police equipment as a gun or a radio.

"The information gets updated in the MDT as you're in route to the scene," said Sgt. Thomas Macartney.

Information is what officers normally see and expect to see on their computer terminal screen. But a week ago Saturday, some of the cops using the 300 newest MDTs had quite a surprise.

They got a pop-up advertisement for a pill similar to Viagra on their screens.

"It was, to say the least, an inappropriate pop-up for a police department to see," said Deputy Commissioner Charles Brennan. "Most of the officers took it as fake and I think they actually got kind of a chuckle out of it."

Brennan is in charge of scientific and technical services for the Philadelphia Police Department. He says the department's computer provider, Verizon, accidentally left open a wireless connection to the Internet on some computers.

"We believe that an officer got out to the Internet, got a pop-up ad and then drug that pop-up ad back into our infrastructure, and the pop-up ad actually duplicated itself on several dozen computers," said Brennan.

The pop-ups didn't affect police response time and Brennan says this does not indicate that the system is vulnerable to hackers. "The most secure information that we have doesn't go over the wireless network. That goes over wired lines, which are linked through another encrypted network. Even if someone got in, they would have to know the encryption key we're using so they would just see a bunch of encrypted data. They wouldn't know what it meant."

Brennan says the pop-up ad was eliminated from the system and Verizon is in the process of checking the new MDTs to make sure that the wireless connection to the Internet is disconnected.