Officials said the organisation, which is searching for a new head after Dominique Strauss-Kahn was arrested in New York last month and accused of sexual assault, has been hit before but the latest attack was more significant and sophisticated.

A spokesman said that the incident was being investigated and the fund was "fully functional". It is believed the attack involved a method known as "spear phishing" in which an individual is tricked into clicking on a bogus Web link.



The IMF collects sensitive information about the financial systems of its 187 member nations. If leaked, some data in IMF computer systems could be used to manipulate or profit from bonds and currencies around the world.

Tom Kellermann, a former cybersecurity specialist at the World Bank who has been tracking the incident, told the "Wall Street Journal" that the infiltration involved significant reconnaissance before the actual attack and code written specifically to penetrate the IMF.

"This isn't malware you've seen before," he said. It was much more difficult to detect and the concern was hackers intended to gather information that could have moved markets. He added that attackers appeared to have broad access giving them sight of IMF plans relating to bailing out the economies of countries.

The IMF has been a central player in the bailout programmes for Ireland, Greece and Portugal and holds sensitive data on other countries that may be edging towards crisis. Its database contains details of negotiations with national leaders as they hammer out the terms of international bailouts.

Staff at the IMF were told of the attack in an internal memo last Wednesday from Jonathan Palmer, the IMF's Chief Information Officer. It said that suspicious file transfers had taken place and that an investigation had shown a desktop computer "had been compromised and used to access some Fund systems".

The memo stated: "At this point, we have no reason to believe that any personal information was sought for fraud purposes."

Mohan Koo, a cyber security specialist who is managing director of Dtex Systems (UK) said that a recent spate of attacks on large global organisations showed that hacking was carefully planned rather than opportunistic.

"Perhaps most frightening of all is the fact that these type of attacks could quite easily be directed towards Critical National Infrastructure (CNI) organisations, for example energy and water, where the impact of such a breach would have severe, immediate and potentially life-threatening consequences for everyday citizens."

Last week, Leon Panetta, the CIA director, told Congress on June 9 that the United States faced the "real possibility" of a devastating cyber attack on the electricity grid, security, financial and governmental systems.

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