US banks have been buffeted by more than a week of powerful cyberattacks, but the mystery surrounding their perpetrators lingers.

One expert said on Friday that he was suspicious of claims of responsibility purportedly made by Islamists angry at an anti-Muslim movie made in the United States, explaining that the widely-circulated internet postings might have been an attempt to deflect attention from the true culprit.

"In the intelligence world, we call that a 'false flag,'" said Mike Smith, whose web security company Akamai has helped analyse some of the attacks.

The concept of cyber crime is not totally different from the concept of conventional crime. Both include conduct whether act or omission, which cause breach of rules of law and counterbalanced by the permit of the state.

Crime is a social and economic phenomenon and is as old as the human society. Crime is a legal concept and has the sanction of the law. Crime or an offence is “a legal wrong that can be followed by criminal proceedings which may result into punishment.” The hallmark of criminality is that, it is breach of the criminal law.