The FBI is investigating a cyber attack against another Democratic Party group, which may be related to an earlier hack against the Democratic National Committee, four people familiar with the matter told Reuters.
The previously unreported incident at the Democratic Congressional Campaign Committee, or DCCC, and its potential ties to Russian hackers are likely to heighten accusations, so far unproven, that Moscow is attempting to meddle in the U.S. election campaign to help Republican presidential nominee Donald Trump.
Hacking of the party's emails caused discord among Democrats at the party's convention in Philadelphia this week where Hillary Clinton was set to accept the party's presidential nomination on Thursday evening.
The newly disclosed breach at the DCCC may have been intended to gather information about donors, rather than to steal money, the sources said on Thursday.
The DCCC raises money for Democrats running for seats in the U.S. House of Representatives. The intrusion at the group could have begun as recently as June, two of the sources told Reuters.
That was when a bogus website was registered with a name closely resembling that of a main donation site connected to the DCCC. For some time, internet traffic associated with donations that was supposed to go to a company that processes campaign donations instead went to the bogus site, two sources said.
The sources said the Internet Protocol address of the spurious site resembled one used by Russian government-linked hackers suspected in the breach of the DNC, the body that sets strategy and raises money for the Democratic Party nationwide.
Cyber security experts and U.S. officials have said there was evidence that Russia engineered the DNC hack to release sensitive party emails in order to influence the U.S. presidential election.
The release of the emails by activist group WikiLeaks caused uproar in the party because they appeared to show favoritism within the DNC for Clinton over U.S. Senator Bernie Sanders of Vermont, who ran a close race for the nomination for the Nov. 8 election. The committee is supposed to be neutral.
The DNC and the DCCC share the same office space on South Capitol Street in Washington.
The DCCC and donation processing company ActBlue had no comment on Thursday. CrowdStrike, the California-based cyber security firm that investigated the DNC breach, declined to comment.
Russian officials dismissed allegations of Moscow's involvement in hacks of U.S. political groups. "It is so absurd it borders on total stupidity," Kremlin spokesman Dmitry Peskov said on Thursday.
Some Democratic officials have accused Russia of hacking the DNC emails in order to help Trump win the race for the White House.
"It's no coincidence someone is hacking into Democratic Party computers. It's almost sounding like a repeat of Watergate," Gilberto Hinojosa, the chairman of the Texas Democrats said, after Reuters reported the DCCC hacking.
"This is just the kind of dirty politics we expect from Donald Trump. I have no doubt Donald Trump is behind it," he said, citing the businessman's praise of Russian President Vladimir Putin and his recent remarks about Russia and Clinton's deleted emails.
Trump angered Democrats this week by inviting Russia to unearth tens of thousands of emails from rival Clinton's tenure as U.S. secretary of state. Trump said on Thursday his comment was meant to be sarcastic.
Jim Manley, a Democratic strategist who once worked for Senate Minority Leader Harry Reid, said the possibility of the DCCC being hacked was cause for great concern.
“Until proven otherwise, I would suggest that everyone involved with the campaign committee operate under the assumption Russians have access to everything in their computer systems,” Manley said.
The FBI referred questions about the DCCC attack to a statement it made on Monday about the DNC hack:
"The FBI is investigating a cyber intrusion involving the DNC and are working to determine the nature and scope of the matter. A compromise of this nature is something we take very seriously, and the FBI will continue to investigate and hold accountable those who pose a threat in cyberspace."
Director of National Intelligence James Clapper said on Thursday the U.S. intelligence community was not ready to "make the call on attribution" as to who was responsible for the DNC hack. The White House said earlier the FBI had not disclosed any information about who was behind it.
Clapper, speaking at the Aspen Security Forum, acknowledged that, "There’s just a few usual suspects out there" who might be responsible for the cyber intrusion, suggesting it was the work of a state actor rather than an independent hacking group.
Clapper said in May he was aware of attempted hacks on campaigns and related groups and he expected to see more as the November election neared. The last two U.S. presidential cycles in 2008 and 2012 witnessed a barrage of cyber attacks from a range of adversaries targeting President Barack Obama's campaign and the campaigns of his Republican foes, officials have said.