Blockchain technology has gained significant attention in recent years due to its potential to revolutionize various industries by providing a decentralized and secure environment for conducting transactions and implementing distributed applications. Decentralized applications (DApps) are based on arbitrary programs (called smart contracts) that can execute a transaction if some specific predefined conditions are met, in order to eliminate the need to rely on trusted third parties. However, as blockchain-based distributed applications continue to proliferate, so do the security challenges associated with this emerging technology. This paper aims to provide an overview of the security issues faced by DApps built on blockchain platforms. An analysis of the security issues for all different layers (smart contract, Dapp, user wallet) was performed. Attacks that take advantage of a single layer or a combination of those are discussed and solutions are proposed for the detection and mitigation of those attacks.