CNN  — 

The US intelligence community has briefed presidential campaigns on potential cybersecurity and espionage issues they may face ahead of the 2020 election.

The briefings, which were unclassified, covered basic cybersecurity hygiene and how to recognize ways that foreign influence operations might try to affect their campaigns. According to a joint statement, the three agencies that administered the briefings – the FBI, Department of Homeland Security and Office of the Director of National Intelligence – “discussed best practices for mitigating risks.”

The agencies declined to say which campaigns attended, but every presidential campaign that registered with the Federal Election Commission was invited, as well as the parties themselves.

According to the joint statement, the briefings took place Tuesday as a webinar – which had moderate technical difficulties, as at least one had to be rescheduled because of audio problems – and Wednesday in person. They included content from the FBI’s Protected Voices campaign, a series of videos on basic cybersecurity tips, and often lasted an hour or more.

The campaigns for former Housing and Urban Development Secretary Julian Castro and businessman Andrew Yang confirmed they received the briefing. Spokespeople for Sen. Elizabeth Warren of Massachusetts, Sen. Bernie Sanders of Vermont and former Vice President Joe Biden refused to comment. None of the other major campaigns immediately responded to CNN’s requests for comment.

Among the components of elections, campaigns are particularly vulnerable among to foreign hacking operations. Though Russia’s 2016 election interference campaign was multi-pronged, by far its prominent operation was hacking the Democratic National Committee, the Democratic Congressional Campaign Committee and nominee Hillary Clinton’s campaign.

While DHS – and the intelligence community in general – has increased efforts to protect election infrastructure, campaigns and political parties remain largely responsible for their own cybersecurity.