Social networking platform LinkedIn has added new features to its service which allow users' information to be used by third-party advertisers.
Although users are able to forbid the use of their data in this way, the settings are hidden away in the accounts management section of the site, and LinkedIn has not warned users of the change.
Paul Ducklin, head of technology, Asia-Pacific, at security firm Sophos, wrote on his blog that the service will use this feature to show its users apparently endorsing products advertised on its site.
"LinkedIn will mine your usage habits to determine what products and services you're interested in, and then use your name and photo in what amounts to an endorsement for those products and services when they're advertised to other users," he said.
This follows rival platform Facebook's recent decision to make its facial-recognition service default to on, with users having to take action to switch it off.
Sophos has called on Facebook and LinkedIn to change their policies and ensure that privacy settings default to the most secure options.
"[Facebook and LinkedIn should] become truly opt-in – not just on the basis that a new user opts in altogether by joining up in the first place, but on the basis that everything is locked down until a new user opens up each feature," it said.
Hacktivist group Anonymous recently declared its intention to attack Facebook, in part for its recklessness with its users' privacy, and its monetisation of its userbase.
LinkedIn, which became a publicly traded company in June this year, has recently seen a steep drop in its share price.