Iran has rejected reports by the US officials claiming its involvement in hacking into several US banks that include Bank of America, JPMorgan Chase & Co and Citigroup over the past year as part of their broad cyber operation.
Iran Civil Defense Organisation head Gholam Reza Jalali was quoted by Fars news agency as saying: "Iran has not hacked the US banks."
Earlier it was reported that the cyber attacks that begun in late 2011, have mainly been "denial of service" campaigns that had interrupted the websites of banks and corporate networks by overwhelming them with incoming web traffic.
US national security official was cited by NBC News earlier saying that the ongoing cyber attacks that slowed the websites of JPMorgan Chase and Bank of America are being carried out from Iran.
"The distributed denial-of-service (DDoS) attacks, which involve overloading a site with requests, are "significant and ongoing" and intended to cause "functional and significant damage," the official said.
There were also reports that the attacks on the US banks had emanated from Iran, but it is not clear whether they were carried out state, groups working for the government, or "patriotic" citizens.
Following the attacks on banks, the US financial services industry group has alerted banks, brokerages and insurers to be on sharp alert for cyber attacks.