Facebook owner Meta says it has banned seven surveillance companies for targeting users on its platforms.
A new report by Meta says about 50,000 users will receive warnings about the "malicious activities".
It accused surveillance firms of actions like creating fake accounts, befriending targets and using hacking methods to harvest information.
The company accused the companies of targeting individuals including journalists and human rights activists.
It said in its report that some 1,500 pages had been suspended by Meta across Facebook, Instagram and WhatsApp following a months-long investigation.
The companies targeted people in more than 100 countries on behalf of their clients, Meta said.
Thursday's report adds further scrutiny to the surveillance industry, following on from allegations earlier this year about the Pegasus spyware targeting thousands.
Facebook is already taking legal action against the owners of Pegasus - NSO Group - over the alleged spreading of software via WhatsApp. The US government blacklisted the firm and others last month, accusing them of providing spyware for foreign governments to "maliciously target" individuals.
"The surveillance industry is much bigger than just one company, and it's much bigger than just malware-for-hire," Nathaniel Gleicher, head of security policy for Meta, said of the new report.
He added investigators had found targeting that was "indiscriminate" including ordinary members of the public as well as high-profile figures like politicians and human rights advocates.
Among the firms named by Meta was Israeli firm Black Cube, which rose to prominence after it emerged Harvey Weinstein had hired them to spy on women accusing him of sexual assault.
In a statement to Reuters, Black Cube denied undertaking "phishing or hacking" and said all of its agents' activities were "fully compliant with local laws".
Users affected by the activity would get automated warnings they had been impacted without giving specifics, Meta officials said.