SAN FRANCISCO — FireEye, a cybersecurity company that has been involved in a number of prominent investigations, including the 2016 attack on the Democratic National Committee, alerted Facebook in July that it had a problem.

Security analysts at the company noticed a cluster of inauthentic accounts and pages on Facebook that were sharing content from a site called Liberty Front Press. It looked like a news site, but most of its content was stolen from outlets like Politico and CNN. The small amount of original material was written in choppy English.

FireEye’s tip eventually led Facebook to remove 652 fake accounts and pages. And Liberty Front Press, the common thread among much of that sham activity, was linked to state media in Iran, Facebook said on Tuesday.

Facebook’s latest purge of disinformation from its platforms highlighted the key role that cybersecurity outfits are playing in policing the pages of giant social media platforms. For all of their wealth and well-staffed security teams, companies like Facebook often rely on outside firms and researchers for their expertise.