Hackers linked to Anonymous and AntiSec have managed to obtain a "sensitive" conference call between the FBI and the British Scotland Yard - which was held to discuss the collective on January 17th.
The FBI has confirmed the incident, stating that the call "was intended for law enforcement officers only and was illegally obtained."
"A criminal investigation is under way to identify and hold accountable those responsible," the bureau said in an official statement quoted by the Associated Press.
It remains unclear if the hackers intercepted the call or extracted a recording from either the FBI or Scotland Yard networks. However, Sophos security researcher Graham Cluley believes Anonymous was able to secretly access the call after compromising a police investigator's email account.
"The assumption has to be that an Anonymous hacker had access to one of the recipients' email accounts, and thus had secret access to the confidential call," Cluley wrote in a blog post.
"No doubt the police authorities will be appalled to realize that the very people that they are trying to apprehend, could have been tuning in to their internal conversations."
Unsurprisingly, Anonymous isn't saying how it managed to obtain the call, stating only: "The FBI might be curious how we're able to continuously read their internal comms for some time now."
It should be noted that government entities, law enforcement agencies and defense companies have become a favorite target for Anonymous and other hacktivist groups like AntiSec. Indeed, a number of sites were compromised in 2011, including ManTech, IRC Federal, Booz Allen Hamilton, dozens of Texas police departments and Arizona law enforcement officials.