Data protection and privacy is rapidly becoming one of themost important issues on the Internet today. Larger number ofInternet sites are collecting personal information from usersthrough forms, cookies, online registrations, or surveys thanever before. New commercial services are springing up that canexploit the ability of mobile communication service providersto determine the geographic location of their users. The newwireless technologies offer mobility; at the same time theyofferlocation informationthat is being used to provide newlocation-aware services.This licentiate thesis concerns our experience building anew innovative network environment at the IT-University (RoyalInstitute of Technology). It explains how we present the newsecurity challenges that a wireless network raises togetherwith how we confronte and investigate a new form of problemthis type of network presents, namely location privacy.The focus of this work has been on trying to provideunlinkability between the location of wireless users and theiractivities in the Internet. The thesis includes a protocolextension to a pseudonymous IP network architecture developedby the Canadian company Zero Knowledge Systems Inc. called theFreedom System. The proposed extension to Freedom Systempermits a mobile client to seamlessly roam among IP subnetworksand media types whilst being untraceable. By untraceable in thecontext of this thesis we mean the capability of a mobile nodeto concealthe relation between location and personal identifiableinformationfrom third parties whilst the user is on themove. This thesis is composed of four published papers wherethe main results are presented.