Law enforcement has kept tabs on demonstrators since anti-police-brutality protests first broke out after the death of George Floyd.
According to Business Insider, leaked documents reveal police exchanged protesters' Twitter handles.
They also monitored protest plans in private Slack and Telegram channels, and kept lists of people who responded to protest events on Facebook.
Records also show law enforcement focusing heavily on perceived threats against officers' lives posted to social media.
The files were leaked from fusion centers, or agencies that share intelligence reports between state and local police departments.
Hackers leaked the documents to the website DDoSecrets, which describes itself as a publisher that does not participate in hacking.
DDoSecrets then published the hundreds of thousands of files in a data dump titled "BlueLeaks."
