U.S. authorities working with law enforcement partners abroad have shut down the Darkode online forum - a marketplace to purchase and trade hacking hacking tools - and charged 12 people linked to the site.

While the forum's existence was widely known, investigators were unable to penetrate the forum until recently. Darkode had utilized password protections and required referrals to join.

Allegedly, the website was hosted on "bulletproof" web servers that were thought to be impenetrable by law enforcement, The Guardian reported.

U.S. Attorney David Hickton announced the charges in Pittsburgh and called Darkode "a cyber hornet's nest of criminal hackers", according to Reuters.

"Of the roughly 800 criminal Internet forums worldwide, Darkode represented one of the gravest threats to the integrity of data on computers in the United States," he said.

The site, which had roughly 250 to 300 active members, was seized and shut down by authorities on Tuesday as most of the arrests were being made and search warrants were being executed.

Some of the targets were responsible for hacking into Sony's PlayStation Network and Microsoft's Xbox Live which rendered their online services inoperable last Christmas.

Other malware offered on the site was far more sinister, such as "ransomware," a virus that locks a computer network until a ransom is paid to the hacker who installed the program, Fox News reports.

Those charged are accused of crimes including conspiring to commit computer fraud, wire fraud and money laundering, selling and using malware programs that could steal data from computers and cellphones and using "bot" networks to take over computers and send spam email.