Last week, the UK's Greater Manchester Police (GMP) launched a Facebook application — much to the consternation of privacy advocates.
The application is called GMP Updates and provides users with crime news, appeals and missing persons stories.
Individual stories can be shared with a user's contacts and users can add comments to the feed. The application also links users to an external Web site where they can anonymously submit information on crimes or view YouTube videos related to ongoing investigations.
Within a day of launch, 750 people had added the application, the police force said.
The Police force pitched the tool as a way of helping raise public awareness about crimes, and encouraging users to submit relevant information.
However, users who add the application to their Facebook profile may be sharing more information about themselves with the police than they realise, according to Guilherme Roschke, a fellow at the Electronic Privacy Information Center (EPIC).
In a research note, Roschke pointed out that Facebook applications have access to far more information than ordinary users do.
Applications can access this data even if it's been marked as not viewable via Facebook networks such as those relating to geographic area or education, Roschke noted. Photos are viewable by applications even if users have restricted which of their contacts can see the photos.
"Law enforcement use of applications will significantly expand the reach of what law enforcement can see, and also provides a more surreptitious viewing ability," Roschke wrote.
He pointed out that applications such as the GMP Updates can, by default, see what the user sees on Facebook, including information about contacts. Contacts can opt out of this sharing but, by default, it includes information such as education history, work history, profile status, photos, groups and relationship status.
"It's not enough to carefully tune your privacy vis-Ã -vis other Facebook users. You also have to avoid adding in applications like the GMP Updates," Roschke wrote.
At the app launch, assistant chief constable Rob Taylor said: "Greater Manchester Police is proud to be the first force in the country to use this new technology, and it demonstrates our commitment to exploring all avenues available to us to help fight and detect crime."