With the advent of personalized services and devices, like online social networks and smart- phones, a user's (otherwise private or sensitive) information is shared with these platforms. While this sharing of information undoubtedly adds value to the user's experience, it raises some pressing concerns about the user's privacy, or the lack of it.

In this dissertation, we propose three major frameworks designed and implemented specifically to protect the users' privacy on such emerging and highly personalized platforms. The three frameworks are as follows.

1. Twitsper, a wrapper for Twitter that allows user to exchange private messages without hurting Twitter's commercial interest.

2. Hermes, a decentralized social network with architecture the explicit goal of preserving a user's privacy and anonymity (including even their sharing patterns) while minimizing the cost each user incurs due to the decentralized model.

3. ZapDroid, a version of Android that is modified and enhanced specifically for the purpose of detecting and negating the impacts of zombie apps. In the context of our work, zombie apps are unused apps that still run in the background, consuming resources and leaking the users' private information. As an OS, ZapDroid is compatible with any app downloadable from the Google Play Store.