"We're committed to ensuring that our bulk data dumps are not exposed," People Data Labs says on its website. "We're extremely sensitive to this and have multiple white-hat partners who are searching the internet in an effort to find vulnerable data sets and clamp down on them before they are discovered by nefarious actors."

The discovery was previously reported by Wired.

Troia, who made the discovery in October during a routine scan for unprotected data, said he reported the four terabyte trove and its location to the Federal Bureau of Investigation. The server has since been shut down, he said. The FBI didn't immediately responded to requests for comment.

Troia says he doesn't know who left the data on that server, saying it could be malicious hackers or People Data Labs' own customers. He said the discovery of social media accounts would be particularly valuable in the hands of criminal hackers or peddlers of misinformation.

"This is the first time ever that I've seen emails, names and numbers linked with Facebook, Twitter, LinkedIn and Github profiles all in one spot," said Troia, who describes himself as a cybercrime hunter. "There are no passwords related to this data, but having a new, fresh set of passwords isn't that exciting anymore. Having all of this social media stuff in one place is a useful weapon and investigative tool."

READ MORE:

• Benefits pros: Avoid becoming collateral damage in a cyberattack
• How do cyber threats impact public entities?
• 5 cybersecurity threats

Copyright 2019 Bloomberg. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.