Facebook general counsel Colin Stretch told a hearing that Instagram posts by suspect Russian accounts were seen by some 20 million Americans previous year. But, as Recode notes, this tool is limited to showing you the accounts that you directly follow, not the ones that your friends do, so you're going to only get one piece of the pie.
Additionally, the tool puts the onus on users to visit the portal, and assumes they know it exists.
It's another step - and so far, the most user-specific - in an effort to shed light on Russian meddling before and during the presidential election.
Facebook today said: "be creating a portal to enable people on Facebook to learn which of the Internet Research Agency Facebook Pages or Instagram accounts they may have liked or followed between January 2015 and August 2017", which should be available to users by the end of this year.
Facebook on Wednesday said it would let some of its users see whether they liked or followed pages belonging to Russia-linked operatives that sought to sow political divisiveness around the 2016 USA presidential election.
Facebook chief executive Mark Zuckerberg has come out strongly against Russian interference, after first denying that his company had any undue impact on the election in which Donald Trump was elected president.
The new function will show a list of which pages a user liked, and the date they did so.
That's important because paid reach and reshared posts by other users are how numerous 146 million Facebook and Instagram users encountered election interference content. USA lawmakers have separately published some posts. Rather than listing each time the troll farm's posts appeared on a user's timeline, the portal will only show instances of active interaction.
Lawmakers at congressional hearings this month suggested that Facebook might have an obligation to notify people who accessed deceptive foreign government material.