A spokesman for the annual summit, which takes place in Davos, Switzerland, said that the theft of travel and credit card details was an outside job involving the forum's databases.
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News that the details of major figures, such as Bill Gates, former US president Bill Clinton and Palestinian leader Yasser Arafat, had been stolen was revealed in a Swiss newspaper yesterday.
Charles McLean, director of communications and public affairs for the WEF, told ComputerWeekly.com, "An intruder apparently hacked a remnant database, allowing them to accumulate contact information."
The forum has launched a full investigation into the break-in, which will include an audit of its security systems.
According to John Merrett, assistant director of the International Chamber of Commerce's commercial crime bureau and cyber crime unit, the forum should make sure that such sensitive information is not connected to the Internet.
"There are simply too many risks," he said. "The WEF should also make sure that its security measures are always kept updated."