A consortium of US security firms planned to attack WikiLeaks, ahead of disclosures about the Bank of America, the Guardian reported yesterday quoting the hacker collective Anonymous.

Anonymous is said to have unearthed leaked emails apparently suggesting that three private security firms – HBGary Federal, Palantir Technologies and Berico Technologies – put forward a plan to undermine the WikiLeaks site to a law firm which has represented the Bank of America.

BoA, the largest US bank, is thought to be the next target of WikiLeaks releases, said the Guardian

Anonymous began releasing tens of thousands of emails sent by HBGary Federal late last week, after the loose-knit "hacktivist" group attacked the security firm's computer systems.

In a newspaper interview Aaron Barr, the company's chief executive, had claimed to be able to expose senior members of the shadowy internet collective.

The Guardian said that one PowerPoint presentation found by Anonymous, and seen by the paper, apparently details a strategy to undermine WikiLeaks and its supporters by submitting falsified documents to the site and then exposing them as forgeries once they were published.

Another document sent by HBGary Federal to Hunton & Williams, the law firm which has represented the Bank of America, suggests ways to "mitigate effect of adversarial groups" on the US Chamber of Commerce for a fee of $2m (£1.2m).

Plans to undermine perceived supporters of WikiLeaks, including Salon.com reporter Glenn Greenwald and the Guardian's James Ball, have also been revealed, it is claimed,   "Without the support of people like Glenn, WikiLeaks would fold," the presentation said.

Greenwald told the Guardian his initial reaction to the leaked proposals was to "scoff at its absurdity", but "after learning a lot more over the last couple of days, I now take this more seriously – not in terms of my involvement but the broader implications this story highlights".

The Bank of America and the US Chamber of Commerce have said they had not known about the presentations, and that HB Gary Federal was never hired on their behalf.

Penny Leavy, the president of HBGary, an affiliate firm of   HBGary Federal,

told a security conference in San Francisco."Anonymous should be regarded as the criminal group it is. They have shown that they will go after security companies and anyone who works with the government."