CRISISBOOM

Anonymous has no official spokesman but the claims were immediately rejected via the YourAnonNews Twitter account, which is often used by the group to announce events and news Photo: EPA/PANTELIS SAITAS

The claim was immediately rejected by the loosely-linked group of hackers, who accused the National Security Agency of “fear-mongering” after its director, General Keith Alexander, made the claims in the Wall Street Journal.

Hackers also launched a “comments flash mob” attack on the newspaper’s website, and warned “We do not forgive. We do not forget. Expect us!”

Gen Alexander is said to have warned that the hackers could develop the ability to bring about a limited power outage across the United States and beyond within a “year or two”.

In the report, Gen Alexander was said to have briefed the White House and other top officials about the growing threat from Anonymous.

He said that cyber-attackers could disable or damage computer networks linked to national grids across the globe.

The general has not spoken publicly about the supposed fears, but one unnamed industry executive told the newspaper: “The industry is engaged and stepping up widely to respond to emerging cyber threats.

“There is a recognition that there are groups out there like Anonymous, and we are concerned, as are other sectors.”

Anonymous has no official spokesman but the claims were immediately rejected via the YourAnonNews Twitter account, which is often used by the group to announce events and news.

One tweet said: “Why would Anons shut off a power grid? There are ppl on life support / other vital services that rely on it. Try again NSA. #FearMongering.”

Other tweets from the account described the alleged comments from General Alexander as “fear-mongering at its best” and “ridiculous”.

Kollektiv, a German group which is linked to Anonymous, carried out a flash mob attack on a number of Facebook pages operated by the Wall Street Journal’s German edition.

Text posted hundreds of times under various different articles read: “Dear editors of the German Wall Street Journal, You equated Anonymous with Al Quaeda in your February 2012 article and the related coverage.

“With this type of coverage you may be able to stir up fear in the United States, but not in the land of poets and thinkers!

“With this comment, we would like to oppose the deliberate dissemination of false information and express our displeasure with your lobby journalism.

“We are Anonymous. We are millions. We do not forgive. We do not forget. Expect us!”

Individuals and groups have used the Anonymous banner to carry out a series of high profile attacks in recent years, including on the US Justice Department for seeking to close down file-sharing websites, and on banks which withdrew support for the Wikileaks whistleblowing site.

At the weekend, the AnonOps Communications website, which is also linked to Anonymous, announced it would continue its assaults on “corrupt corporate and government systems”. The group has already crippled the websites of the FBI and CIA.