Italian police are making use of Facebook to identify criminal networks and even to catch gangsters who cannot resist posting updates while on the run, L'Espresso weekly reported on Friday.
"For us it is an important tool," Alessandro Giuliano, head of police detectives in Milan, was quoted as saying.
"It shows the interlinkages between people. The photographic material is also a starting point for investigations."
The report gave examples of mafia members using the network to make extortion demands, send death threats and organise home deliveries of drugs, as well as to demonstrate the clout of their social circle.
"It allows us to better understand how they operate," Giuliano said.
Antonello Ardituro, an anti-mafia prosecutor in Naples, said: "Facebook allows you to spread messages in a simple and direct way."
Following an attempt on his life, one suspected mafia member posted a Facebook update: "An eye for an eye, a tooth for a tooth. Show no mercy."
The man's profile revealed he was a fan of the film "Scarface" with Al Pacino and showed a photo of his birthday cake with two chocolate guns.
Police also follow the movements of suspected gangsters with Facebook.
An alleged contract killer who kept checking his Facebook profile was nabbed after police tracked the Internet key he was using to log on.
A leading boss was caught when he posted two photos on his girlfriend's Facebook page that showed he was in Marbella on southern Spanish coast.
Another man was caught in Venezuela where he was trying to organise drug shipments to Europe through the social network using a fake profile.