Officials say the U.S. election system is so secure that no foreign country could alter the results to the extent that they would. Authoritarian adversaries, however, use disinformation and cyberespionage to target campaigns and voters while fueling distrust and discord.

Here’s what you need to know as the presidential election approaches:

Russia is the most active and sophisticated country attempting to manipulate US elections, using fake websites, state-controlled media, and unwitting Americans to spread misleading and polarizing content aimed at undermining confidence in elections.

The Kremlin’s disinformation apparatus addresses controversial issues such as immigration, crime, the economy or disaster relief. The goal, officials said, was to weaken the United States, erode support for Ukraine fighting Russian invaders and reduce America’s ability to counter Russia’s growing ties with China, North Korea and Iran.

Intelligence officials and private security analysts have determined that Russia supported former President Donald Trump and sometimes used AI-generated disinformation to smear his Democratic rival, Vice President Kamala Harris. Trump praised Russian President Vladimir Putin, suggested cutting funding to Ukraine and repeatedly criticized the NATO military alliance.

In one particularly bold campaign, Russia released a video accusing Harris of paralyzing a woman in a car crash years ago. Another video featured fabricated allegations against Harris’ running mate, Minnesota Gov. Tim Walz.

On Friday, the FBI confirmed Moscow’s role in producing a third video showing the destruction of mail-in ballots in Pennsylvania. Local election officials quickly debunked the video as fake.

Russia has also sought to pay American influencers who spread narratives favored by the Kremlin. Last month, U.S. authorities accused two Russian state media employees of funneling $10 million to a Tennessee company to create pro-Russian content. The company later paid off many popular right-wing influencers who said they had no idea their work was supported by Russia.

Moscow’s campaign won’t end on Election Day. Instead, intelligence officials and private security analysts predict that Russia will use allegations of election irregularities to suggest that the results cannot be trusted. A recently declassified intelligence memo stated that Russia may encourage violent protests after the election.

“Putin’s goal is to fuel chaos, division and polarization in our society,” said Michael McFaul, a former US ambassador to Russia who now teaches at Stanford University.

Russia has denied allegations that it tried to influence US elections. A message left at the Russian embassy in Washington was not immediately returned Saturday.

Iran has been a particularly brazen player in foreign intervention this year.

The company is accused of hacking Trump campaign associates and providing stolen communications to media outlets and Democrats in the hope of uncovering damaging stories that could damage Republican prospects. Dirty emails were sent to people affiliated with President Joe Biden’s campaign, but there was no sign of anyone responding, officials said.

The Justice Department last month charged three Iranian hackers at large with a years-long operation that targeted a wide range of victims.

U.S. officials have described the hack as part of a broader effort to interfere with elections that Iran perceives as particularly important. They say Iran has made clear its opposition to the Trump campaign. His administration ended the nuclear deal with Iran, reimposed sanctions and ordered the killing of Iranian General Qassem Soleimani, prompting Iranian leaders to swear revenge.

In addition to cyber operations, U.S. officials have repeatedly expressed concern about the potential for Iran to use violence against Trump or other members of his administration on U.S. soil. In 2022, authorities filed charges related to a thwarted Iranian plot to kill Trump’s national security adviser John Bolton, and this year charged a Pakistani man with ties to Iran with a plot to carry out political assassinations of Trump in the United States.

Leaders in Tehran may seek to encourage violent protests after the election, according to a declassified intelligence memo. Officials say Iran is also secretly financing and supporting protests in the United States about Israel’s war in Gaza.

Iranian officials have denied allegations that the country tried to influence the election. Iran’s mission to the United Nations issued a statement this week that said: “Iran has no intent or purpose to interfere in U.S. elections.”

U.S. intelligence officials believe China is taking a more neutral stance in the election and is focusing on voter contests, targeting candidates from both parties based on their positions on issues key to Beijing, including support for Taiwan.

But the Chinese government has been running a sophisticated hacking operation for years targeting Western life and industry that goes far beyond its electoral impact.

“They want access from the city council to the president,” said Adam Darrah, a former CIA political analyst who is vice president of intelligence at ZeroFox, a cybersecurity firm that tracks foreign online threats.

On Friday, news broke that Chinese hackers had targeted cellphones used by Trump, his vice president, J.D. Vance, and people associated with Harris’ campaign as part of a much broader spying effort. It was not immediately clear what data, if any, was accessed.

A spokesman for the Chinese Embassy in Washington said they were not familiar with the details and could not comment, but maintained that China routinely falls victim to cyber attacks and opposes this activity.

Tough. Foreign adversaries, including those now accused of interfering, have attempted to interfere with varying degrees of success in the past few election cycles.

But the U.S. government, which has been accused of obtaining information about the extent of Russia’s interference in the 2016 election, has sought to aggressively address foreign threats this year as part of an effort to reduce their impact and reassure Americans that the election is secure.

In 2016, Russian military intelligence officers hacked the email accounts of Hillary Clinton’s campaign chairman and the Democratic Party and released tens of thousands of communications in support of Trump’s successful presidential campaign.

That year, Russia also engaged in a massive but covert social media trolling campaign aimed at sowing disagreement on hot social issues, sowing division in the American election process, and damaging Clinton’s bid for the presidency.

The oddities continued during the 2020 election period, when a Ukrainian lawmaker, identified by US officials as an “active Russian agent”, published audio recordings of Democrat Joe Biden, who was running for president at the time.

That same year, Iranian hackers were blamed for emails purporting to come from the far-right group The Proud Boys, which officials said were designed to harm Trump’s candidacy.