Police are keeping a close eye on Facebook in a bid to sniff out potential drug dealers.
The Canterbury organised crime squad has recently sent letters to members of a blackmarket Facebook group warning them their actions are being monitored.
The revelation has raised privacy concerns, but Detective Senior Sergeant Jason Stewart says police have no need to apologise.
"Some people are making very little effort to conceal what they are doing or their identities, and I think if you read through the recent postings, the public are in overall support of us policing this area."
People in the online group received letters saying: "Police have been monitoring your Facebook profile and established that you are engaged in a Facebook group that actively sells and trades in controlled drugs," reports Fairfax.
"Committing offences against [drug laws] can lead to penalties, including imprisonment."
Snt Sgt Stewart told Fairfax the internet is a "public space" and evidence gathered through Facebook is sometimes used to carry out police raids.