Iran denies behind cyber attacks on US banks

"The Islamic republic of Iran categorically denies any involvement in cyber attacks on American banks and denounces such methods which are a violation of the sovereignty of nations," the statement said.

US media reported Wednesday that American financial institutions are being pounded with high-powered cyber attacks that some suspect are being orchestrated by Iran as payback for political sanctions.

"There is no doubt within the US government that Iran is behind these attacks," James Lewis, a former official in the state and commerce departments and now a computer security expert at the Centre for Strategic and International Studies, told the New York Times.

While the identities of those behind the online onslaught officially remain a mystery, it was clear they were using a potent new weapon for slamming bank websites with overwhelming numbers or requests for information, reports said.

The top 20 US banks were hit on Wednesday with a third wave of attacks, each of which has been preceded by a claim of responsibility by a group calling itself Izz ad-Din al-Qassam Cyber Fighters.

The attacks began in September last year, according to Radware, which specializes in commercial computer security and has been investigating the cyber assaults.

John Bumgarner of the US Cyber Consequences Unit, a non-profit group that studies the impact of cyber threats, cautioned against rushing to assign blame for the attacks.

"These attackers are using the anonymity of the cyber space to mask who they are," Bumgarner said. "There is not irrefutable evidence that the Iranian government was responsible."