Computers used by the election campaigns of both Barack Obama and John McCain were broken into earlier this year, and a large number of files related to the evolving policy positions of the two candidates were stolen, a Newsweek magazine story has claimed.

The attacks appear to have been perpetrated by an unidentified "foreign entity" looking to steal information that might be useful in future negotiations with the next American president, Newsweek reported, quoting several unnamed sources.

According to Newsweek , the attacks happened sometime around mid-year and were reported to the Obama and McCain campaigns by the US Secret Service , the FBI and even the White House.

The story doesn't detail how the feds learned about the intrusions but says they assured the Obama camp that the break-ins didn't appear to be the work of his political opponents. Obama's team was also informed that the McCain campaign's computers had similarly been broken into, the story says.

A spokesman in McCain's press office said that he didn't have any information about the reported breaching of the Arizona senator's campaign systems. Obama's press office didn't immediately respond to inquiries about the Newsweek story.

But the former director of technology for the 2004 presidential campaign of Dennis Kucinich voiced skepticism about some of the claims made in the story and said that it omits some important information.

For example, it isn't clear from the story whether the servers running the campaign websites were broken into or if the hacking targeted other systems, such as email servers, said Henry Poole, who now is a partner at CivicActions LLC, a firm that offers Internet campaign consulting services.

It's unlikely that either campaign would have stored sensitive data on the same servers that were being used for public campaigning purposes, Poole said. Typically, he added, all e-commerce activity on campaign websites - including online donations - is heavily secured, while other portions of the sites may not be as well protected. "It wasn't clear to me at all what was compromised," he said.

In addition, while it's understandable that the FBI and Secret Service would be involved in investigating such intrusions, it isn't at all clear why the White House would be involved, Poole said.

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.