Some government witnesses do only what they must to help. Others do everything they can. Hector Xavier Monsegur, who was known as "Sabu" in hacking circles, was the latter.

According to unsealed court documents released last week and obtained by the Wall Street Journal, Monsegur was "proactively" cooperating with the FBI, helping the government agency build its cases against alleged hackers. Monsegur's work with the government became an around-the-clock job, as he stayed up all night at times coaxing alleged hackers into conversations that were recorded and eventually used against them by the FBI.

Sabu's true identity was revealed earlier last week when the US Attorney announced that government agencies had arrested six individuals both in the US and abroad with alleged ties to hacking groups LulzSec, Anonymous and AntiSec. One government official told CNET that "hackers should know if they are here or abroad, their anonymity won't last forever".

The arrests have likely forced hackers around the world to start looking over their shoulders. The individuals who were arrested had allegedly been operating under the radar for quite some time. It was Monsegur's efforts, investigators say, that helped lead them to the arrested individuals.

But Monsegur's participation did more than just target alleged hackers. According to the court documents, he also helped the FBI identify "upwards of two dozen vulnerabilities" that his alleged colleagues had discovered. After turning that information over to the FBI, the agency was able to inform companies of their security holes and patch them before a hack occurred.

Speaking to the Wall Street Journal, an unidentified source said that Monsegur's information helped the FBI stop over 300 planned hacks.

Still, Monsegur isn't necessarily out of the woods just yet. His initial charges, to which he pleaded guilty in August, could have seen him get 124 years in prison. Since he became an informant, it's likely that he was offered some sort of plea deal, but at a press conference announcing the arrests last week, US attorneys would not confirm that was the case.

Via CNET