Is it possible to find out who is interested in you or in a particular person online? Is it possible to detect who is looking for someones name, for someones address or for some similar private information about a particular person, maybe on Google or Facebook? There are many reasons why someone is looking for personal information about someone else. To identify who is interested in a particular person could have some advantages for this person. Finding out that somebody is interested in your CV could be useful when looking for a job. On the other hand, finding out that somebody is looking for your address could be very helpful if this someone is a debt collector. Nowadays it is important to control private data which is stored or redistributed on the World Wide Web. This thesis is about finding people or machines that work with private data of an individual online. An additional goal is to have more control over this data and at the same time to have more control over privacy that is becoming more and more violated.