# A Survey on Consensus Protocols and Attacks on Blockchain Technology
## 8 Prevention Measures for Attacks  
In [93], the authors reviewed the blockchain concept and relevant issues, as well as a thorough examination of probable security assaults and existing results that can be used as countermeasures. In this article, they also reviewed many ways to improve blockchain security by summarizing key aspects that may be used to create security tools and blockchain systems that address security problems. Finally, the study covers outstanding concerns and future research paths in blockchain IoT systems. Using real-world examples, the authors of this review paper thoroughly examined many assaults on blockchains as well as blockchain security issues. Furthermore, while delving into these concerns in a variety of ways, this article examined the numerous security issues, weaknesses, and assaults that hamper the further adoption of blockchain technology. They also covered a variety of other blockchain applications and benefits, as well as significant business potential. Finally, they summarized existing security solutions for diverse situations as well as research challenges that have yet to be tackled. [PERSON] and [PERSON] [94] conducted a comprehensive study on blockchain technology, focusing on popular consensus algorithms in order to determine their features and the factors that affect security and performance. Furthermore, they awarded the consensus algorithm a categorization. They addressed in depth the consensus algorithm that was researched, as well as an analysis of the main elements affecting these algorithms, and they have referred to certain recommendations that must be considered and can help the growth of this area. In [95], the authors propose a novel architecture that detects and prevents malevolent activities of collaboration inside the blockchain node. They demonstrated how the smart contract conducts identification and authentication of rogue nodes by setting up a blockchain network in the lab separately for proof of concept. They assessed the performance on the following classifications of attacks:  
(a) Attempts to bring the blockchain down  
(b) Attempts to put invalid data into the database  
(c) Attempts to hijack unauthorized data  
They also measure the time it takes to identify an attack to assess the architecture's performance. According to the data, the proposed architecture offers a good likelihood of identifying and isolating insider harmful behavior [63]. In [96], according to this study, blockchain is a popular technology for dealing with transactions that require high levels of security. This technology provides and complies with the secure operation and handling and crucial security considerations are required. There are several flaws that potentially lead to some of the attacks that have been found. Even though blockchain is cohesive with existing security technologies, appropriate technology must be invented to overcome these risks and attacks. To summarize, consensus mechanisms, private key security obtained through public-key encryption schemes, illegal activity caused by cryptocurrency applications, double spending obtained through transaction authentication procedures and transaction privacy effluence obtained through a transaction design stream, and sinner smart contracts caused by smart contract applications may all pose significant risks to blockchain 1.0 and 2.0. Other dangers to blockchain 2.0 include smart contract vulnerabilities caused by a program design problem, under-optimized smart contracts caused by a program writing flaw, and under-priced processes caused by an EVM design flaw. We can simply argue that they are all linked because most attacks provide room for subsequent attacks. In [97], [PERSON] et al. propose a blockchain-based tracking solution for insider threats. To begin, this research creates an insider network model from a unique viewpoint that intercepts insider attackers from escaping and its forensics. They then look at why locating attackers and gathering authentication during an insider threat is so difficult.