Data Privacy and Integrity (Unauthorized Access to Devices)

Data privacy and security are the most prudent issues that trip up the interconnected digitized world. The data stored in IoT devices is vulnerable to cyberattack, since it is shared, transmitted, and processed through multiple IoT devices. This can lead to unauthorized access to IoT networks, causing data theft and data manipulation by adversaries. Such events can compromise data privacy and integrity. To leverage such threats, blockchain can be a viable solution [40]. Blockchain uses a decentralized model that adopts cryptographic hash functions to prevent data tampering. Furthermore, blockchain maintains reliability and trustworthiness, due to its immutable nature [41].

IoT Device Authentication

Verified devices need to join a network to prevent malicious intruders. The diverse heterogeneity of devices and services in an IoT network requires different mechanisms for authentication. For this reason, there are no standard global security protocols. This poses difficulty for the authentication and authorization techniques of IoT devices. Blockchain can provide unique identifiers for IoT devices using cryptographic hash algorithms. It prevents any unauthorized IoT devices to gain access and attempt any malicious communication. A transaction made by a sender can be signed by using a unique public key [42].

Insecure Devices

The vast number of embedded devices in an IoT network are mostly devices with low cost and low power. These devices have limitations in terms of memory and computing power. Attackers can gain easy access to such physically insecure devices. Blockchain provides credentials as unique key pairs for each of the registered connected IoT devices. The absence of the intermediary in blockchain reduces the risk of device tampering and other malicious activities. Moreover, smart contracts in blockchain keep track of the node that needs to patch hardware, or update or reset IoT devices.

Sybil Attacks

A Sybil attack is a critical security attack in an IoT environment, where a malicious node attempts to masquerade as other nodes in the network, resulting in multiple fake identities. It helps an attacker to gain unauthorized access to the system and impede routing messages, disrupting the overlay of network operations. Sybil attacks can be addressed by blockchain technology. Generating a PoW for the mining process is very expensive, because this is a complex mathematical calculation. Yet, it can prevent malicious nodes from creating multiple fake identities. On the other hand, PoS provides a consensus based on the staking currency of each miner, which can limit the resource requirements for Sybil attacks [43].

Software Attack (Malware and Ransomware)

Malware (viruses, spyware, Trojan horses, etc.) is malicious software exploited by hackers to damage a computer system and steal confidential information. Ransomware is a variation of malware that can limit or completely lock down user access to files in a network by encrypting them and asking for a ransom in exchange for the decryption keys. Using blockchain, the whole database of sensitive data can be encrypted and stored in a digital ledger. The database is shared among all available nodes in the network, and consensus algorithms validate each transaction. This makes it almost impossible for an attacker to take over a single node and hold it for ransom, because multiple access points are available. This further prevents a single point of failure.

RPL Routing Attack

RPL is a routing protocol that transmits data packets between a sender node and a sink node, creating a destination-oriented directed acyclic graph (DODAG) [44]. The sink node is the centralized root node known as 6LBR (6L0WPAN Border Router). This centralized structure can be vulnerable to a potential single point of failure. As a decentralized ledger, blockchain eliminates the risk of a single point of failure, providing a distributed trust. All control frames are timestamped in the blocks of the blockchain with an encrypted hash of the previous block. This ensures secure data packet transmission and mitigates eavesdropping or man-in-the-middle attacks.

Sinkhole and Wormhole Attack

In this attack, a compromised end in the network attracts neighboring nodes with appealing fake routes for transferring their data packets toward the destination. This results in the dropping of the data packets midway, creating a sinkhole [45].

A wormhole attack is also an active attack, where two compromised nodes strategically place themselves at two ends of the network, creating a tunnel. This tunnel gives a false impression of being the active shortcut route of low-latency for data transfer [46]. Thus, nodes prefer to choose this route over any other routes, causing selective data forwarding, eavesdropping, and network disruption. The blockchain network enables controlled message flow through the network. The message is also encrypted in the blocks using cryptographic hashes and digital signature, which ensures data integrity and correct path selection.

Malicious Code Injection

This is a severe attack, where an attacker either physically inserts a harmful code via some exterior device to steal user data or injects a malicious program into the system. This compromises a node and causes the entire network to shut down [47]. To perform this attack, an external device must first be connected to the IoT network. Blockchain can ensure the authorization of such devices by providing cryptographically secured unique identifiers to each IoT device. This prevents malicious device communication. Smart contracts can be used to validate and authenticate the code transactions, preventing the network from injecting malicious programs [48].


Jamming is a type of attack on wireless networks that aims to disrupt operations by flooding the network with an illegitimate radio frequency (RF). For this reason, a legitimate data packet cannot be transmitted, which causes an IoT service malfunction [49]. The cryptographic features (consensus algorithms) of blockchain could be a probable solution. Legitimate data packets can be encrypted for temper-proofing and to ensure data integrity.

Spoofing Attack

Spoofing is a technique adopted by potential attackers to forge device or user identities, to gain unauthorized access and launch malicious attacks. The forms of spoofing attacks include IP spoofing, email spoofing, DNS spoofing, etc. Blockchain could maximize security against such attacks. Each sender node can use digital signatures to sign a transaction before sending it to the blockchain network, to establish legitimate access control. Furthermore, smart contracts can facilitate secure message communication, device authentication, and authorization [50].

Deviation and Disruption of Protocols

This type of attack compromises standard protocols, such as application protocols, network protocols, and key management protocols. This results in service unavailability [51]. Blockchain provides soft and hard fork improvements of the standard protocols via the cryptocurrency community. It reduces the overhead computational cost of devices having limited memory and computational power [52]. Decentralization omits the necessity of a third party, which provides autonomy, transparency, trust, and the prevention of disrupting protocols. Moreover, blockchains store cryptographic hashes that aid in the verification of each device [53].

The Exploitation of Misconfigurations (OS, Servers, Frameworks, etc.)

A secure application requires the security of its various OS platforms, frameworks, servers, database management systems, etc. A loophole in the configuration of any of these components leaves the application vulnerable to attacks. Examples of such scenarios include attackers with unauthorized access of disabled directory listings to exploit configuration files, and improper handling of error logs. This can expose sensitive information related to underlying application flaws, and exploitation of default account credentials (root, passworded) [54]. Since blockchain is immutable, it prevents the unauthorized modification of configuration files stored in the ledger. It also incorporates cryptographically enforced smart contracts that ensure the secure execution, monitoring, and management of configuration files automatically, in a tamper-proof environment [55].

Single Point of Failure

The heterogeneity of IoT network devices requires cloud identification and verification services for connection and data storage. The cloud is a trusted entity for the verification of data in the entire network, which makes it vulnerable to a single point of failure. This gives rise to critical data security and privacy issues. A tamper-proof environment for a sustainable network is a necessity for the IoT services envisioned. Blockchain’s decentralized system prevents IoT devices from undergoing a single point of failure, since a digital ledger of transactions is open to every node for proper validation and authentication [56].

Table 8.2 summarizes various security issues and challenges in IoT systems. The table highlights the security challenges of the IoT, attack strategies adopted by attackers, the effects, and possible blockchain solutions [57] against those attacks.

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