A new report by Mashable.com said chats on Facebook are being watched for clues of illegal activity.
The social website monitors for words or phrases that might be a hint that a suer is up to something.
"The vast majority of scanning of private conversations is done electronically. It's not done by humans," said Ken Colburn of Data Doctors.
"A human only gets involved when the automated mechanism spits out a transaction that it deems a human should take a look at it."
Facebook security then decides whether to contact police.
Colburn said that what Facebook is doing is legal. "Once [your chat message] is committed to a digital form, it can be monitored, tracked, copied and duplicated in the blink of an eye," said Colburn.
"I think users, in general, have to really understand that."
In fact, Facebook may not have any choice but to check chats for criminal activity.
"A lot of what Facebook is going through in this area is being forced or pushed just from some of the legal obligations or potential liability they have by not participating or turning folks in," Colburn said.