After linking China to a series of cyber attacks on US government agencies and companies last February, security firm Mandiant has now implicated Iran as the brains behind the newest wave of cyber espionage in the US.

Mandiant chief security officer Richard Bejtlich said that a previously unidentified hacking organization has been traced to be based in Iran and has reportedly infiltrated the cyber networks of at least one US corporation.

This Iranian group, according to Mandiant, had surfaced in the last six months.

''You're starting to see the Iranians get more active,'' Bejtlich said.

''We've got at least one case where we think it's Iran, and we think what they are doing is trying to gain some experience on a live network.''

Bejtlich's comments validate earlier assertions made by some US politicians, including Republican House chairman on intelligence committee Mike Rogers, that the recent cyber attacks in the US have been initiated by some Iranian groups.

Mandiant said it is still investigating the movements of this new group and has not yet fully concluded if they are backed by the Iranian government.

''We don't know if they're patriotic hackers,'' Betjlich said.

He also would not confirm which US corporation has been under attack by this group.

''We haven't seen these guys before,'' Bejtlich said. ''They are working their way through a network trying to figure out where they can they go, who will find them, who will stop them.''

Meanwhile, Alireza Miryusefi, Iran's spokesperson to the United Nations has called the allegations "baseless" and has denied any participation of the Iranian government in the alleged cyber attacks.

It was just last February when Mandiant exposed China's People's Liberation Army as the group behind the cyber hacking of at least 141 companies all over the world since 2006.