Media reports say hackers backed by the Russian government stole highly sensitive U.S. espionage tools in 2015 after a U.S. National Security Agency (NSA) contractor placed the classified materials on his home computer.
U.S. authorities believe the alleged theft, first reported by The Wall Street Journal on October 5, may have been carried out by exploiting antivirus software made by the Moscow-based company Kaspersky Lab, several media outlets reported, citing unidentified sources.
Washington last month banned U.S. federal agencies from using Kaspersky products, citing alleged "ties between certain Kaspersky officials and Russian intelligence and other government agencies."
The Kremlin has condemned the ban, and company founder Eugene Kaspersky has repeatedly denied that his company, one of Russia's most successful technology firms, has links to Russian intelligence.
The reports on the alleged NSA theft said that the hack handed information to Russia on how the U.S. spy agency breaches foreign computer networks and defends itself against cyberattacks.
The NSA did not comment on the reports.
The NSA contractor, who has not been publicly identified, has been cooperating with U.S. federal authorities, the reports quoted unidentified sources as saying.
The reports could heighten tensions further between Russia and the United States, which accuses the Kremlin of directing a hacking and propaganda campaign aimed at influencing last year's presidential election. Moscow rejects the allegation.
Kaspersky Lab responded to The Wall Street Journal report in an October 5 statement, saying that it "has not been provided any evidence substantiating the company's involvement in the alleged incident."
"It is unfortunate that news coverage of unproven claims continue to perpetuate accusations about the company," it said, adding that the firm "does not have inappropriate ties to any government, including Russia."
"The only conclusion seems to be that Kaspersky Lab is caught in the middle of a geopolitical fight," the statement said.
The report triggered statements of concern from both Democratic and Republican senators.
U.S. Senator Ben Sasse (Republican-Nebraska), a member of the Senate Armed Services Committee, said that if the report was true, "the NSA needs to get its head out of the sand and solve its contractor problem. Russia is a clear adversary in cyberspace and we can't afford these self-inflicted injuries."
Russia has granted asylum to former NSA contractor Edward Snowden, who leaked a trove of classified U.S. documents on government surveillance in 2013.
U.S. Senator Jeanne Shaheen (Democrat-New Hampshire), a top advocate in Congress for banning government use of Kaspersky Lab products, urged the Trump administration in an October 5 statement to declassify information about purported threats posed by the Russian firm.
"It's a disservice to the public and our national security to continue withholding this information," Shaheen said.