The relevant work was divided into four groups. Twitterize and FaceCloak are among the extensions that make the use of existing \acp{OSN} more secure. Twitterize forms an overlay network for hashtags on Twitter that allows secure and anonymous communication. The browser extension Facecloak protects privacy by transmitting fake data to the Facebook servers, which are recognized when displayed and replaced by the real data. The decentralized social networks diaspora* and LifeSocial promise the protection of data through their decentralized design. The LifeSocial application creates a \ac{P2P} network among the participants, so no additional servers are necessary. Each user provides resources so that the network scales automatically. The diaspora* application runs on servers and is accessible via a web front end. Each user can operate his own diaspora* instance and thus manage his data. Emerging technologies like blockchain and cryptocurrencies are used to create \acp{dApp}. In this chapter two social network \acp{dApp} AKASHA and Peepeth were introduced. Both use the Ethereum blockchain and the IPFS protocol to store data. Finally, the ActivityPub protocol was presented, which defines communication in decentralized social networks.