WASHINGTON — American intelligence officials have seen an uptick in Russian disinformation about mail-in ballots as President Trump has escalated his attacks on voting by mail, Representative Adam B. Schiff, the Democratic chairman of the House Intelligence Committee, said in an interview.
American intelligence agencies have not explicitly linked the increase in Russian disinformation operations to the president’s comments. They would not make such an link without specific intelligence about the Kremlin’s marching orders. Intelligence and other officials acknowledged that Russia always focuses its disinformation efforts on existing controversies to amplify ongoing arguments.
Mr. Trump’s false assertions have also fueled the spread of misperceptions about widespread mail-in voting. Experts have repeatedly said absentee voting is secure, and there was little public controversy over it until the president began his attacks.
After Mr. Trump began stepping up his criticism of mail-in voting, Mr. Schiff, Democrat of California, asked the intelligence agencies he has oversight over to track any rise in Russian disinformation efforts.
“Sure enough, it wasn’t long before the intelligence community started seeing exactly that,” Mr. Schiff said. “It was too enticing and predictable an option for the Russians. They have been amplifying Trump’s false attacks on absentee voting.”
Intelligence officials have said they have seen no attempts by the Russians or other foreign powers to interfere with mail-in voting, spread fake ballots or change absentee vote counts.
Last week, Christopher A. Wray, the F.B.I. director, told lawmakers he saw no coordinated voter fraud effort. He has also warned about Russian disinformation efforts aimed at benefiting Mr. Trump’s re-election.
On Monday, the F.B.I. and the Homeland Security Department’s Cybersecurity and Infrastructure Security Agency warned about foreign intelligence services and hackers spreading disinformation about voting systems to undermine confidence in the election.
Hackers have been spreading false information about compromised voting systems in an attempt to manipulate public opinion and cast doubt on the integrity of the election, according to the new warning.
Mr. Schiff predicted that if the presidential vote is close and counting absentee ballots takes time, Russia and other foreign powers would most likely step up their disinformation campaigns, amplifying Mr. Trump’s criticism of mail-in votes and accusations of a rigged election.
“The Russians will almost certainly emphasize the president’s false charges and cause as much chaos in the American streets as they can,” Mr. Schiff said.
Russia has denied — and mocked — American claims it is intervening in the election or using cyberattacks to influence the vote. In recent days it has been pushing for international prohibition on cyberattacks, without addressing its own role. On Monday, Russian officials highlighted a new article by Sergey V. Lavrov, the Russian foreign minister, that argued the world was facing “a real cyberpandemic,” a rash of cyberattacks on health care, fiscal and education establishments.
The federal government, in its Monday warning, said the best way for Americans to insulate themselves from disinformation around the election is to seek information from trustworthy sources and ”view early, unverified claims with a healthy dose of skepticism.”
Some cybersecurity experts have said that foreign actors may try to disrupt state and local websites around the election to try to restrict the flow of accurate information. Others security experts believe a wave of ransomware-style attacks on local governments could also amplify disinformation campaigns to sow doubt about voting systems.
“I am not sure the direct attacks will be so widespread that they can directly affect a specific vote on any widespread basis,” said Karl Sigler, a senior security research manager with Trustwave, a cybersecurity company. “But the damage to public trust is a hard thing to get back.”
The F.B.I. and the Cybersecurity and Infrastructure Security Agency have been closely monitoring state and local voting systems, stepping up efforts to track attempted intrusions.
Because voting is done on a local level, the election infrastructure is fairly resilient, and it would be extraordinarily difficult for a foreign attacker to hack enough local governments to change the results of state or national elections.
But eroding confidence in the election does not require Russia or another foreign power to change a single vote. Mr. Schiff said it was far easier for adversaries to cause “Americans to doubt that they can rely on the results of the election.”
“They don’t actually need to change the votes, they just need to diminish voters’ confidence that the votes are accurate,” Mr. Schiff said. “The Russians have concluded it is easier to change the voters than the vote.”