Do you think, having an FBI agent as a friend on Facebook is cool? Maybe, but all the criminals boasting about their exploits will be in for a shock.

Us federal law enforcement agents are said to be going undercover with false online profiles in the social-networking sites – including Facebook, Linkedln, MySpace and Twitter – to search for evidence and witnesses in criminal cases, and in some instances, track suspects, and communicate with suspects and gather private information and communication map.

An internal Justice Department document obtained by the civil liberties group, Electronic Frontier Foundation, in a Freedom of Information Act lawsuit, describes the value of social networking sites to the government investigators.

According to the Associate Press, the document says Facebook is “often cooperative with emergency requests” from federal investigators while Twitter’s layers demand a warrant or subpoena before it will turn over customer information.

The document makes clear that U.S. agents are already logging on surreptitiously to exchange messages with suspects, identify a target’s friends or relatives and browse private information such as postings, personal photographs and video clips.

Among other purposes: Investigators can check suspects’ alibis by comparing stories told to police with tweets sent at the same time about their whereabouts. Online photos from a suspicious spending spree — people posing with jewelry, guns or fancy cars — can link suspects or their friends to robberies or burglaries, according to the source.

[Source: The Associate Press]