Clinton campaign also hacked in attacks on Democrats

The latest attack, which was disclosed to Reuters on July 29, follows reports of two other hacks on the Democratic National Committee, or DNC, and the party’s fundraising committee for candidates for the U.S. House of Representatives.

A Clinton campaign spokesman said in a statement late on Friday that an analytics data program maintained by the DNC and used by the campaign and a number of other entities "was accessed as part of the DNC hack."

"Our campaign computer system has been under review by outside cyber security experts. To date, they have found no evidence that our internal systems have been compromised," said Clinton campaign spokesman Nick Merrill.

The U.S. Department of Justice national security division is investigating whether cyber attacks on Democratic political organizations threatened U.S. security, sources familiar with the matter said on July 29.

The involvement of the Justice Department’s national security division is a sign that the Obama administration has concluded that the hacking was sponsored by a state, people with knowledge of the investigation said.

Hackers, whom U.S. intelligence officials have concluded were Russian, gained access to the entire network of the fundraising Democratic Congressional Campaign Committee, or DCCC, said people familiar with the matter, detailing the extent of the breach to Reuters for the first time.

Cyber security experts and U.S. officials said earlier this week they had concluded, based on analysis of malware and other aspects of the DNC hack, that Russia engineered the release of hacked Democratic Party emails to influence the U.S. presidential election.

The U.S. Federal Bureau of Investigation said on July 29 it was "aware of media reporting on cyber intrusions involving multiple political entities, and is working to determine the accuracy, nature and scope of these matters."

"The FBI takes seriously any allegations of intrusions, and we will continue to hold accountable those who pose a threat in cyberspace," the agency said in an emailed statement.

It was not immediately clear what Clinton campaign information could have been accessible to hackers, or how the compromised "analytics data program" was used.

The hack did not involve the private email system Clinton used while she was secretary of state.