Members of the AntiSec hacking campaign claim to have compromised more than 10GB of information belonging to US police organisations.
The group said in a posting that it had taken down more than 70 police sites as the first in a series of attacks in response to the recent arrests of 16 people allegedly involved with an Anonymous-backed attack on PayPal.
"Your bogus trumped-up charges against the Anonymous PayPal LOIC attacks will not stick, nor will your intimidation tactics stop us from exposing your corruption," police were told in a statement announcing the breach.
"While many of the recent 'Anonymous' arrestees are completely innocent, there is no such thing as an innocent cop, and we will act accordingly."
In addition to the site takedowns, AntiSec hackers have harvested account information on 7,000 law enforcement officers, and taken more than 10GB worth of data from law enforcement group servers. The archive is said to include internal information on Anonymous informants and tipsters.
Additionally, the group says it will release police email archives and documents taken from police academy training systems.
The breach comes as law enforcement groups step up their efforts to apprehend members of Anonymous and LulzSec.
In July, authorities in the UK arrested 18 year-old Jake Davis on five charges. The Shetland teenager is accused of acting as an unofficial spokesperson for Anonymous and LulzSec under the name 'Topiary'.
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