What is Denial-of-Service (DoS) Attack?

A denial-of-service attack happens when a computer or network service becomes temporarily inaccessible to its users. These attacks are widely used by hackers to intrude upon the regular processing of computer systems and services.

The act is carried out by overloading the targeted host or network with data until it crashes. This might last anywhere from a few hours to several months and can be especially time and money consuming.

There can be different denial-of-service attacks depending on their business and type:

• Volumetric attacks take place by absorbing the whole bandwidth capacity of a network and overloading it with echo requests.
• Fragmentation attacks are looking for ways to infiltrate the target network's built-in reassembling capabilities.
• Syn flooding attacks are not far from volumetric attacks, nevertheless, the attacker quickly establishes a link to a server without finalizing it.
• Phasing attacks focus on irreversibly damaging the target network by sending a fake update request and adding malware throughout the network.
• Application layer attack carries out by bombarding the victim with inquiries and targeting undiscovered programming faults in an application or network.
• A distributed denial-of-service attack is the most prevalent type of attack, which is categorized as a malware attack. Hackers distribute malware to networks of linked devices and begin blasting them with massive amounts of requests in order to overflow the network.

At the same time blockchain technology applications appeared, a new kind of DoS, a blockchain denial-of-service (BDoS) attack arose. These types of attacks are aimed at blockchains that function under the proof-of-work consensus algorithm.

It operates by targeting the reward system for miners. The PoW consensus algorithm depends on miners to manually validate new blocks. If the attack takes place, miners do not gain their rewards, and the block validation process is disrupted. 

Nevertheless, it is way more complicated to carry out a DoS attack on a decentralized network.

Typically, DoS attacks depend on the centralized characteristic of traditional networks, but this approach does not work with blockchain-based networks. Attackers transmit fraudulent proofs to the blockchain claiming they have a mining lead in order to successfully disrupt the mining activity.

This discourages other miners from performing operations necessary for transaction validation, which essentially slows down the processing power of the blockchain significantly. Even so, BDoS attacks have been extremely rare and unsuccessful so far.

Sadly, as cryptocurrency exchanges become more popular, they are subjected to a growing number of DDoS attacks. Since 2020, many distinct DDoS attacks have been attempted against some of the most prominent cryptocurrency exchanges.

This causes the exchange's services to be unreachable for an extended length of time.