Messaging app WhatsApp reported banning more than 400,000 accounts that breached its terms of service in Brazil during last year's general elections.
The information was disclosed by the company in a document submitted to authorities to support an investigation into the spread of misinformation during the presidential campaign.
According to the company, the accounts were banned between August 15 and October 28, 2018. In its still unknown which candidates would have been potentially benefited or harmed as a result of mass messaging through the app.
In a statement to lawmakers, WhatsApp said it "expressly forbids the use of any application or robot to send mass messages or to create accounts or groups in unauthorized or automated ways."
"Because WhatsApp is an encrypted platform, our decisions against automated and bulk messaging activities are based on account behavior rather than messaging content," the company explained.
The company also noted that it has "significantly enhanced" the app to limit viral message spread, with message forwarding capped to five conversations at a time. It is also using 'forwarded' and 'highly forwarded' labels to help users identify non-personal content.
The campaign that led to the election of current president Jair Bolsonaro has been linked to a defamatory scheme whereby businesses were accused to have contracted a multimillion-dollar blast messaging service to attack his opponent.
Local electoral legislation only allows use of contact lists drawn up voluntarily by the campaigns themselves. Business campaign funding is also prohibited in the country, which would deem the entire operation illegal.
When WhatsApp capped message forwarding, president Jair Bolsonaro's son, congressman Eduardo Bolsonaro, criticized the app's decision and said he would move to other platforms such as Telegram to communicate with the supporter base.
The family is understood to have been advised by Donald Trump's former campaign strategist, Steve Bannon.