Hillary Clinton's presidential campaign said Friday that an "analytics data program" maintained by the Democratic National Committee had been hacked but that its computer system had not been compromised, denying news reports Friday that the campaign had become the third Democratic Party organization whose systems had been penetrated.
So far, campaign computer experts "have found no evidence that our internal systems have been compromised," campaign spokesman Nick Merrill said in a statement.
Merrill said that "an analytics data program maintained by the DNC and used by our campaign and a number of other entities was accessed as part of the DNC hack." Campaign officials did not immediately respond to requests for further information about the data program.
Earlier in the week, the Washington Post was told that the campaign — like many other political organizations — had been attacked by would-be hackers this year but that there was no evidence that any of the attacks had succeeded.
FBI agents visited the Clinton campaign in the spring and described attempts to break into its system. Campaign security consultants were aware of the attacks and concurred that none appeared to have been successful.
U.S. officials believe that the same Russian intelligence agency, the GRU, successfully hacked into the DNC and the Democratic Congressional Campaign Committee.
Senior figures in the national security community are warning that the Russian hack of the DNC and subsequent release of committee emails by the antisecrecy group WikiLeaks may be part of a broader attack on the U.S. electoral process.
The emails appeared to show an effort by DNC officials to help Clinton over her rivals in the Democratic primaries, and the release led to the resignation of the committee's chairwoman, Rep. Debbie Wasserman Schultz, of Florida.
If the email leak was orchestrated by the Russian government, "this is an attack not on one party but on the integrity of American democracy," the Aspen Institute Homeland Security Group, a group of 32 homeland security and counterterrorism experts, said in a statement.
"And it may not be the end of such attacks," said the group, which includes a former CIA director and a homeland security secretary. "It is not unthinkable that those responsible will steal and release more files, and even salt the files they release with plausible forgeries."
The FBI issued a statement Friday about the reported hacks.
"The FBI is 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 statement said. "The cyber threat environment continues to evolve as cyber actors target all sectors and their data. The FBI takes seriously any allegations of intrusions, and we will continue to hold accountable those who pose a threat in cyberspace."
The GRU apparently stole not only DNC emails, but also opposition research files on GOP candidate Donald Trump, according to private investigators. Russian government hackers also have targeted computer systems at the Trump campaign, the Republican National Committee and GOP political action committees, among others, law enforcement officials said, but it is unclear if they were successfully breached.
Some lawmakers warned that the operation — if the GRU role is confirmed — appears to have moved beyond traditional espionage into information warfare.
"Now that the precedent has been set of operationalizing the mass leaking of the information, we're in a whole new dangerous ballgame, with a level of brazen interference that we haven't seen before," said Rep. Adam Schiff of California, the ranking Democrat on the House Intelligence Committee.
Russian officials have dismissed reports of involvement by its intelligence services.
Lawmakers and security experts have called on the Obama administration to ensure that responsibility for the DNC hack and leak is assigned. Schiff and Sen. Dianne Feinstein of California, the ranking Democrat on the Senate Intelligence Committee, urged the administration to make public as much information as possible about the incident while protecting sources and methods to illuminate potential Russian motivations for "what would be an unprecedented interference in a U.S. presidential race."
The Aspen Group warned that election officials at every level of government "should take this lesson to heart: Our electoral process could be a target for reckless foreign governments and terrorist groups."
Members of the group also raised the specter of foreign groups manipulating election results.
"What would be very troubling would be somebody hacking into the actual voting databases or network systems in which ballots are sent to the central database, and either altering results or raising questions about the integrity of the results," said Michael Chertoff, former homeland security secretary. "That would take the 'hanging chad' debacle of 2000 and make it seem trivial. This would become an issue of electronic hanging chads."