According to the Newsweek story, a federal agent told Obama campaign officials that they had an IT security problem "way bigger than what you understand. You have been compromised, and a serious amount of files have been loaded off your system."
Technical staffers working for Obama later speculated that the hackers might have been from China or Russia, the story says. It adds that a security firm retained by the campaign later plugged the security holes.
The attacks reported by Newsweek aren't the first time that Obama's campaign computers had been broken into during the run-up to the election. In April, a cross-site scripting vulnerability in the social networking section of Obama's Web site was exploited by a hacker who redirected visitors to the Web site of Democratic rival Senator Hillary Clinton. That attack prompted the Obama campaign to take steps to strengthen the security of its site.
McCain's running mate, Alaska Governor Sarah Palin, also became a cyber-target earlier this year, when the son of a Tennessee state legislator allegedly hacked into her Yahoo e-mail account to see if he could find anything incriminating about the vice presidential candidate. And early last month, Republican officials disclosed that a laptop containing "strategic information" had been stolen from a McCain campaign field office in Missouri.