Hackers operating under the Anonymous banner have claimed responsibility for an attack on the US Department of Justice website.
The hackers claimed responsibility for the attack via messages on Twitter, Pastebin and YouTube on Saturday.
The messages promised that the site's defacement was the start of a wider attack, pledging to publish information stolen during the cyber raid at a later date.
At the time of publishing the Justice Department had not responded to V3's request for comment on the attack and Anonymous' claims.
The attack was listed as being a part of the Anonymous collective's wider #OpLastResort campaign.
The campaign was started earlier in January in protest at the treatment of internet activist and Reddit founder Aaron Swartz, who died earlier this month.
Swartz had faced trial on charges that he used the Massachusetts Institute of Technology's computer networks to steal over four million articles from the JSTOR online archive and journal distribution service.
If found guilty he faced up to 31 years in jail and a potential $1m fine. Security experts have since questioned the hackers' claims.
Sophos senior technology consultant Graham Cluley added that there is no way to tell the authenticity of the claims.
"The claims that they have got their hands on sensitive US government information and plan to release it, it's impossible for us to verify," Cluley told V3.
"We'll just have to wait and see. In the past many claims have been made under the banner of ‘Anonymous' - some of them have turned out to be true, and some of them have turned out to be false."
F-Secure security researcher Sean Sullivan agreed that at present it was only clear that the attack was a web site defacement.
Sullivan warned that further attacks similar to the one on the Justice Department will likely continue to be mounted under the #OpLastResort banner for the foreseeable future.
"Such defacements will undoubtedly continue. But if activists continue to call them attacks, and continue to make unsubstantiated claims, they have less and less impact," he told V3.