Users of social media are constantly warned to watch what they reveal online. You never know who might read your postings, the argument goes — your grandmother, your boss, potential employers.

To that list of potential readers, you'll have to add the police, at least if you live in Britain.

Wired UK reports that London's Metropolitan Police, or Scotland Yard in popular parlance, has admitted the existence of a team dedicated to monitoring the social media postings of some 9,000 people for signs of political unrest.

The unit has 17 officers and uses what it calls Social Media Intelligence, or SocMint, to scan Facebook, Twitter, YouTube and other social media services 24 hours a day, Wired UK said, adding that the team is developing special tools to smooth the process.

As part of the Metropolitan Police, the unit has jurisdiction in all of England and Wales, and some jurisdiction in the legally distinct "countries" of Scotland and Northern Ireland.

At a security conference in Australia last month, a Scotland Yard official, Umut Ertogral, spoke freely during what he thought was a closed-door meeting.

Social media "almost acts like CCTV [closed-circuit television] on the ground for us, really," Ertogral said, according to the Australian Financial Review.