Just 33 days ahead of the election, a top Justice Department official is warning of an "onslaught of foreign election interference" from Russia, Iran and China.

Matthew Olsen, head of the department's National Security Division, said in an interview with CBS News that the U.S. is facing a multi-pronged offensive from the three nations. Among the lines of attack is a barrage of propaganda from Russia to sow division in a highly polarized U.S. electorate, persistent cyber-intrusions into the campaigns of both former President Donald Trump and Vice president Kamala Harris, and a "grave" Iranian assassination plot targeting Trump.

"They see this as a period of vulnerability for us," Olsen told CBS Evening News Anchor and Managing Editor Norah O'Donnell. "They are looking at ways at which they can change the outcome of our election, or to find issues that divide us in ways that support their national interests at the expense of ours."

Olsen's comments are expected to be the Justice Department's last word on the subject of election interference, honoring a policy of refraining from public statements in the 30 days before an election to avoid influencing the outcome.

In a wide-ranging interview, he characterized the threats as "sophisticated," utilizing advanced technology "to target our politics."

In Russia, he says malicious actors are leveraging artificial intelligence to manufacture content, such as fake videos of the vice president meant to spread disinformation. Moreover, he said, Moscow has upped its game in another way –laundering Kremlin talking points through U.S.-based social media influencers who have large online followings. Olsen described a brazen effort by Russia to help Trump win the election.

"What we're seeing with Russia is clearly a preferred outcome," Olsen said. "Russia has been seeking to boost the candidacy of the former president and to denigrate the candidacy of the vice president."

Contrary to messaging from the Trump campaign, which has consistently disputed reports of Kremlin interference, Olsen said the Russian initiative was real in 2016, and is even more robust now.

"Russian interference in the [2016] election was not a hoax. It was actually happening then. It is actually happening now," Olsen said. "There is no question about it."

Olsen said the intelligence and law enforcement communities learned a lesson from 2016, when officials were highly protective of the intelligence indicating the Russians were aggressively meddling in the election. This cycle they made a conscious decision to be far more transparent with the public.

"We've learned at the Justice Department, but this especially true for the intelligence community, and that is to be as open and transparent as we possibly can about the nature of the threat," Olsen said.

In September, the Justice Department seized 32 internet domains they say Russia used as part of their "doppelganger" online campaigns aimed at influencing elections worldwide, including the upcoming presidential election here in the U.S. Olsen pointed to the case as an example of ways the department is working to "dismantle the infrastructure" of Russia's propaganda operation.

The seizure targeted Russian entities, including the Social Design Agency (SDA), which since 2022 has allegedly been responsible for coming up with the propaganda strategy that included impersonating legitimate news entities, like Fox News or the Washington Post.

"They created these fake websites. They look very real," Olsen said. "It is hard for the average American to understand the sophistication of these efforts. But that's why we're trying to be as transparent as possible about the nature of the threat."

Olsen pointed to a specific case brought by the Justice Department where they uncovered "talking points" of people "at the highest level of the Kremlin, people within [Vladimir Putin's] inner circle" who have stated their goal of Trump prevailing.

Olsen said that in addition to its goal of bolstering Trump's campaign, Russia is closely focused on sowing division among American voters on hot-button issues. Chief among them is the war in Ukraine, where Moscow is intent on diminishing popular support among Americans for Ukrainian independence.

But Olsen said that the Russians also see domestic issues as ripe targets for its disinformation campaign. He pointed to immigration, one of the most contentious policy fights in the 2024 election. The Russians, he said, are "highlighting immigration as a wedge issue."

Russia is not the only country looking to "sow discord" ahead of the election. Among the Justice Department's biggest worries, according to Olsen, is credible evidence that Iran wants to "compromise" Trump's campaign and is actively plotting to assassinate Trump, something that he says they are monitoring "with intense focus."

"Among the countries in the world, there are few countries that pose the range and significance of threats that Iran does," Olsen said, noting that this effort is related to the death of Iranian General Qasem Soleimani, who was killed by an American airstrike in 2020. "They are determined to retaliate for Soleimani's killing. And they have targeted U.S. officials who they believe are responsible for that decision."

In the past few months there were two attempts on former President Trump's life, and in a separate case, a Pakistani national with ties to Iran was charged with allegedly plotting a murder-for-hire scheme targeting current and former U.S. officials –a list that sources familiar with the investigation told CBS News may have included Trump.

Olsen declined to comment about whether the government's case against Ryan Wesley Routh, who has been charged with attempting to assassinate the former president at his Florida golf course in September, has any ties to a foreign government, citing the ongoing nature of the case. Routh has pled not guilty.

Last month, the Office of the Director of National Intelligence briefed Trump on "real and specific threats from Iran to assassinate him."

As for China, while the volume of activity is less than that coming out of Iran and Russia, their interest in the upcoming election seems more focused on congressional and state office campaigns, where they aim to find candidates who may fall "more in line with the interests of China," rather than the presidential race.

Olsen said he hasn't seen any foreign efforts to manipulate voting machines or other election infrastructure. But one of his biggest worries is what happens in the aftermath of the election, particularly given the likely delays in determining the vote results.

"I do think that our adversaries will continue to see this time period as an opportunity for them to shape the outcome of the election or to sow discord within the country," Olsen said, warning, "that is really the biggest issue that I see right now."

and contributed to this report.