The International Monetary¹ Fund (IMF) says it has been targeted by a sophisticated cyber attack.

国际货币基金组织称其遭受了一场复杂的网络袭击。

Officials at the fund gave few details but said the attack earlier this year had been "a very major breach²" of its systems, the New York Times reports.

Cyber security officials said the hack³ was designed to install software to create a "digital insider presence".

The IMF, which holds sensitive economic data about many countries, said its operations were fully⁴ functional⁵.

The cyber attack took place over several months, and happened before former IMF chief Dominique Strauss-Kahn was arrested over sexual assault charges.

"I can confirm that we are investigating an incident," said spokesman David Hawley.

"I am not in a position to elaborate（详细描述） further on the extent of the cyber security incident."

The New York Times said IMF staff had been told of the intrusion（侵入，闯入） on Wednesday by e-mail, but that the Fund had not made a public announcement.

The e-mail warned that "suspicious file transfers" had been detected and that an investigation⁶ had shown a desktop⁷ at the Fund had been "compromised and used to access some Fund systems".

There was "no reason to believe that any personal information was sought for fraud purposes," it said.

High profile breaches⁸

A cyber security expert told Reuters the infiltration⁹（渗透） had been a targeted attack, which installed software designed to give a nation state a "digital insider presence" at the IMF.

"The code was developed and released for this purpose," said Tom Kellerman, who has worked for the Fund.

Bloomberg quoted an unnamed security expert as saying the hackers¹⁰ were connected to a foreign government; however such attacks are very difficult to trace.

The World Bank said it briefly¹¹ cut its network connection with the Fund out "an abundance of caution".

"The World Bank Group, like any other large organisation¹², is increasingly aware of potential threats to the security of our information system and we are constantly working to improve our defences," said spokesman Rich Mills.

The incident is the latest in a string of high profile cyber security breaches.

In April, the Sony Playstation network was shut down after hackers stole the personal data of about 100 million accounts and in May, US defence firm Lockheed Martin said it had come under a significant cyber-attack.

CIA Director Leon Panetta told the US Congress earlier this week that a large-scale cyber attack while would cripples（削弱） power, finance, security and governmental systems was "a real possibility in today's world".