Hackers with ties to Russia, China and Iran are attempting to spy on people and groups involved with the US 2020 presidential election, Microsoft says.
The Russian group which hacked the 2016 Democratic campaign is again involved in cyber-attacks, said the tech firm.
Microsoft said it was “clear that foreign activity groups have stepped up their efforts” targeting the election.
Both President Donald Trump and Democrat Joe Biden’s campaigns are being targeted.
Russian hackers from the Strontium group have targeted more than 200 organisations, many of which are linked to US political parties – both Republicans and Democrats, Microsoft said in a statement.
“Similar to what we observed in 2016, Strontium is launching campaigns to harvest people’s log-in credentials or compromise their accounts, presumably to aid in intelligence gathering or disruption operations,” said Tom Burt, a Microsoft vice-president in charge of customer security and trust.
The firm said Chinese hackers had launched attacks targeting individuals connected to Mr Biden’s campaign, while Iranian hackers had continued efforts targeting people associated with the Trump campaign.
Most of the cyber-attacks had not been successful, according to Microsoft.
The report comes a day after a whistleblower at the US Department of Homeland Security alleged he was put under pressure to downplay the threat of Russian interference in the election as it “made the president look bad”.