Social networks admit sharing user data with advertisers

Ad agencies have been receiving names or profile IDs of users clicking on adverts

A number of social networking companies, including Facebook and MySpace, have been accused of giving advertising companies access to users' personal data.

Facebook and MySpace have admitted to sharing the data, which could be used to trace the individuals clicking on certain adverts. Both social networks have claimed that they are working to resolve the problem.

It is normal practice for advertisers to be given details of address pages from which users click on adverts, but the URL cannot normally be linked back to an individual.

However, the advertising agencies have been receiving the names or profile ID numbers of those who click on their adverts because social networks tend to personalise URLs on users' pages.

This could allow the advertising companies to track down other details about the individual, such as age and interests, depending on how much profile information the user has decided to make public.

The actions appear to show a flagrant disregard for the terms and conditions in which social networks promise not to share user information with advertisers without prior consent.

Facebook defended its actions, however, claiming that the user IDs passed to advertising agencies did not contain "personally identifiable information".

The social networking firm said that, if advertisers wanted to look for other details about users, they would first have to gain their consent.

Facebook has now said that it has been working on ways to remove user IDs in referral URLs.

MySpace, meanwhile, did not appear to recognise any data privacy problems. A spokesman said that access to a MySpace FriendID does not permit access to information beyond that which the user has already made public.

The company did not acknowledge the need for its users' ad-clicking activity to be kept separate from their profile.

MySpace also said that it is currently implementing a way to obfuscate the FriendID in any URL passed to advertisers.