Web Search Engines (WSEs) are basic tools for finding and accessing data in the internet. However, they also put the privacy of their users at risk. This happens because users frequently reveal private information in their queries. WSEs gather this personal data and build user profiles which are used to provide Personalized Search (PS). PS improves the users' search results and, hence, it is a key element for the successfulness of WSEs: the entity that offers the best searching experience should attract more users. Nevertheless, profiles can also be used in an improper way by WSEs or they can be stolen by attackers.