How Did Feds Listen In on Blagojevich? Investigators normally use wiretaps, "surreptitious entry" to listen to targets.

Dec. 11, 2008 -- Court records from the investigation into Illinois Gov. Rod Blagojevich are filled with recorded conversations of the governor allegedly offering to sell an appointment to President-elect Barack Obama's former U.S. Senate seat. How did the government find out what he was saying?

Federal investigators tapped Blagojevich's home phone and bugged his personal office and a conference room in the Friends of Blagojevich campaign headquarters. Officials began listening to conversations in late October, the court documents say.

Former law enforcement officials and security experts, who were not familiar with the details of the investigation, said it may be easier than one would think to listen in on private conversations, even those of a governor.

Blagojevich was arrested Tuesday on corruption charges. He was released on bond and has denied any wrongdoing.

While it was not immediately clear how the FBI and federal prosecutors accessed Blagojevich's campaign offices, law enforcement officers have at times gone to extraordinary lengths to spy on the targets of their investigations.

"It's not something you do overnight. You have plenty of time to develop probable cause. You do a survey, figure out how to get in," said Lee Flosi, a former FBI agent who headed the Chicago Organized Crime Task Force.

In order to get a federal wiretap, investigators must get approval from the Department of Justice and a federal judge. They must have probable cause that the wiretap will detect ongoing criminal activity, according to former law enforcement officials.

With a court order, investigators could listen to conversations on Blagojevich's home phone by working through the phone company and without having to enter his home.

The bugs in the campaign offices would be more difficult, former investigators say, and might have required investigators to make stealth entries to plant the listening devices.

"Typically what they will do is surreptitious entries," said Brad Garrett, a former FBI agent and ABC News consultant.

Though every situation is different, Flosi said agents will often pose as repairmen or try to get a job with a night cleaning crew. On other occasions, agents have broken into buildings.

"You might have to pick the lock and disable the alarm," said Garrett. "The key is to get in and out, and nobody knows that you've done it."

Wiretaps Tiny, But Sometimes Detected

During one undercover operation, Flosi said, agents wanted to get into a house that was across the street from a police station. Flosi said he hid inside an empty refrigerator box, and agents posing as deliverymen left the box on the front doorstep, obscuring the view from the police station.

He said he picked the lock from inside the box. Once the door was unlocked, the other agents removed the box and they were able to walk into the home's unlocked door later to plant the bug.

"It's amazing to me how easy it is to get into most places," said Kevin Murray, a security consultant. "Locks and alarms are not really good enough to deter espionage."

Listening devices can be very small and easily concealed, with some so tiny they can "fit underneath your fingernail," said Murray. Bugs have been placed inside walls, in light fixtures, lamps, phones and coasters.

John Gotti held secret meetings in an apartment above the Ravenite Social Club in New York's Little Italy that belonged to the widow of a former mob associate. When the widow left home to spend Thanksgiving with relatives, the FBI placed a bug in the living room of her apartment and recorded hours of Gotti's conversations.

But bugs are not always successful, and have at times been detected.

Reputed mobster Louie "Ha Ha" Attanasio famously took a sledge hammer to a parking meter outside a social club in Brooklyn where members of the Gambino crime family congregated after learning that the police had managed to bug it.

"I've had people call me and say, 'come pick up your equipment,'" said one former federal prosecutor.

Blagojevich apparently suspected some of his conversations could be recorded, allegedly telling one associate to talk as if the whole world were listening -- a missive recorded by investigators. Apparently, he was right.