Bosses of the data firm Cambridge Analytica were secretly filmed by Britain's Channel 4 News describing their efforts to help Donald Trump win the US election in 2016.

CEO Alexander Nix, who was suspended Tuesday, and colleagues detailed the level of the work they undertook, as well as the shadowy online tools they weaponized against Hillary Clinton, the 2016 Democratic presidential nominee.

They revealed how they used groups outside of Trump's official Republican vehicle to seed attack ads — something that may pique the interest of US authorities.

Clinton has questioned whether Cambridge Analytica was involved in Russia's interference in the election.

The bosses of the data firm Cambridge Analytica were secretly filmed boasting about using shadowy online propaganda tools to help Donald Trump win the US presidential election in 2016.

The footage is the latest revelation from an explosive investigation by Britain's Channel 4 News, which sent an undercover reporter into meetings with Cambridge Analytica over four months.

Last week, the embattled company was suspended from Facebook for harvesting the data of 50 million users.

CEO Alexander Nix and his colleagues thought they were talking to a fixer for a wealthy client hoping to get candidates elected in Sri Lanka when they met the Channel 4 News reporter at luxury hotels in London.

In one exchange, Nix said he had met Trump "many times" and described what the firm undertook for his campaign.

"We did all the research, all the data, all the analytics, all the targeting — we ran all the digital campaign, the television campaign, and our data informed all the strategy," Nix said.

In another conversation, Cambridge Analytica's chief data officer, Alexander Tayler, argued that the firm's work helped Trump emerge victorious.

"When you think about the fact that Donald Trump lost the popular vote by 3 million votes but won the Electoral College vote, that's down to the data and the research," he said.

A Cambridge Analytica spokesman told Channel 4 News: "CA has never claimed it won the election for President Trump. This is patently absurd."

Nix was suspended on Tuesday pending an independent investigation by the British barrister Julian Malins, the company said in a statement.

The board said his recorded comments "do not represent the values or operations of the firm, and his suspension reflects the seriousness with which we view this violation."

'We just put information into the bloodstream to the internet, and then watch it grow'

Nix and his colleagues described to the undercover reporter how Cambridge Analytica disseminated Trump's message online without leaving a trace.

Mark Turnbull, the managing director of Cambridge Analytica Political Global, was filmed saying the firm would use proxy organizations, such as charities or activist groups, to discreetly funnel negative material about other candidates onto social media.

Nix, right, with Mark Turnbull, another Cambridge Analytica executive. Channel 4 News

"We just put information into the bloodstream to the internet, and then watch it grow, give it a little push every now and again over time to watch it take shape," he said. "And so this stuff infiltrates the online community and expands, but with no branding, so it's unattributable, untrackable."

Nix said Cambridge Analytica also used ProtonMail, taking advantage of the encrypted email service's "self-destruct" feature that deletes messages within two hours of being read.

"There's no evidence, there's no paper trail, there's nothing," Nix said.

A Cambridge Analytica spokesman said that using encrypted communications was a common practice.

"We take information security with the utmost seriousness, and for high-profile clients, using mainstream email providers simply doesn't provide a suitable level of security," he said.

Cambridge used super PACs to seed attack ads

Cambridge Analytica's bosses also described how they used groups outside Trump's official Republican vehicle to seed attack ads — something that may pique the interest of US authorities.

They explained how they would use super PACs — independent campaigning committees not constrained by certain spending rules — to target Hillary Clinton, the 2016 Democratic presidential nominee.

The "Defeat Crooked Hillary" YouTube channel. YouTube

"So the campaign will use their finite resources for things like persuasion and mobilization, and then they leave the 'air war,' they call it, like the negative attack ads, to other affiliated groups," Tayler said.

Turnbull explained how Cambridge Analytica created the "Defeat Crooked Hillary" attack ads, which Channel 4 News said were funded by the Make America Number 1 super PAC and watched more than 30 million times during the campaign.

Coordination between an official campaign and these outside groups is illegal under US election law, Channel 4 News said.

Cambridge Analytica has insisted that it has strict rules to separate its activity and that it was transparent about its work on political campaigns and PACs.

"We have strict firewall practices to ensure no coordination between regulated groups, including the teams working on non-coordinated campaigns being physically separated, using different servers and being banned from communicating with each other," a spokesman said.

Clinton: Did Cambridge Analytica coordinate with Russia?

Speaking to Channel 4 News while promoting her book last year, Clinton questioned whether Cambridge Analytica was involved in Russia's interference in the 2016 US election.

Hillary Clinton. Lisa Lake/Getty Images for Geisinger Symposium

"So you've got Cambridge Analytica, you've got the Republican National Committee — which, of course, had always done data collection and analysis — and you've got the Russians," she said. "And the real question is how did the Russians know how to target their messages so precisely to undecided voters in Wisconsin or Michigan or Pennsylvania; that is really the nub of the question.

"So if they were getting advice from, let's say, Cambridge Analytica or someone else about 'OK, here are the 12 voters in this town in Wisconsin — that's whose Facebook pages you need to be on to send these messages,' that indeed would be very disturbing."

A Cambridge Analytica spokesman denied any involvement in Russia's election interference, saying that "such an allegation is entirely false."