As people's lives become more reliant on Online Social Networks (OSN), ensuring the security and protection of their personal information has become critical. These platforms expose users to possible security flaws and privacy violations, like identity theft, even while they provide a variety of tools for communication and interest sharing. This paper is a survey paper that examines the security concerns of online social networks, such as Sybil attacks, in which phony identities threaten integrity; identity theft, which exploits personal information; and de-anonymization, which exposes user identities. Furthermore, it provides a thorough examination of Blockchain technology as a dependable solution to these security issues. Furthermore, this study finds the best secure solutions by evaluating various Blockchain platforms such as Steem, Hive, Sapien, and Ethereum. The findings reveal that Blockchain technology provides a robust and effective security framework for safeguarding online social networks, offering enhanced protection against various OSN attacks.