Simply put, a DoS attack, or denial of service attack, is a method used to disrupt legitimate users' access to target network or website resources. Typically this is accomplished by overloading a target with large amounts of traffic (typically a website server), or by sending malicious requests that cause the target resource to malfunction or crash entirely.

The first recorded denial of service attack occurred in February 2000, when a 15-year-old Canadian hacker used this attack to attack Amazon and eBay web servers. Since then, DoS attacks have been increasingly used to compromise targets (websites) across many industries.

Types of DoS attacks

Some types of DoS attacks are designed to damage specific Targets access to a network or resource, while other types aim to make the resource completely inaccessible. These attacks can last from minutes to hours, and in rare cases, days. Disruption of these network resources often results in significant financial harm to the businesses being targeted, and there are few mitigation strategies in place.

DoS attacks come in many different forms and scales. Since not all devices and networks are attacked in the same way, those seeking to compromise need to be creative and exploit every possible vulnerability in a system's configuration.

Some well-known DoS attack types include:

Buffer overflow attack

The most common type of exploit, a buffer overflow attack relies on sending more traffic to a target than the developer originally built the system to handle. This type of attack allows the attacker to completely crash the target or take control of the target's processes.

ICMP flood attack

ICMP flood attack targets misconfigured devices on the target network , forcing the computer to distribute fake packets to every node (computer) on the target network instead of a single node, thus overloading the network. This attack can often be called a "Ping of Death" or a "smurf attack."

SYN flood attack

SYN flood attack sends a connection request to the (target) network server, but never fully authenticates the connection. It will then continue (send requests) to all remaining open ports on the target network server until it forces a server-side crash.

DoS attack vs. DDoS attack

Another similar term you may encounter is DDoS attack , which stands for Distributed Denial of Service Attack. The difference between DoS and DDoS attacks is that many malicious computers are directed against a single resource. Distributed denial-of-service attacks are more likely to successfully compromise their targets than single-source DoS attacks. Attackers prefer this approach because since attacks come from multiple points, it becomes harder to trace the source of the attack.

Will DDoS attacks affect cryptocurrencies?

In most cases, denial-of-service attacks are used against the web servers of large businesses, such as banks, online retailers, and even government and public services - however, there are things to consider Any device, server or network connected to the internet can be a potential target for these types of attacks.

With the development of cryptocurrency in recent years, cryptocurrency exchanges have become increasingly popular targets for DDoS attacks. For example, when the cryptocurrency Bitcoin Gold was officially launched, it immediately became the target of a massive DDoS attack that ended up disrupting their website for many hours.

However, the decentralization of blockchain provides strong protection against DDoS and other cyber attacks. Even if multiple nodes cannot communicate or are offline, the blockchain can continue to operate and verify transactions. When the interrupted nodes come back to work, they resynchronize and catch up with the latest data provided by the unaffected nodes.

The degree of protection each blockchain has against these attacks is related to the number of nodes and hash rate of the network. As the oldest and largest cryptocurrency, Bitcoin is considered the most secure and resilient blockchain. This means DDoS and other cyberattacks are less likely to cause it to crash.

The proof-of-work algorithm ensures that all network data is protected through cryptographic proofs. This means that previously verified blocks are almost impossible to change. Changing the Bitcoin blockchain would require recording the entire structure piece-by-piece, which would be impossible even with the most powerful computers in the world.

Thus, a successful attack can only modify a few recent blocks of transactions within a short period of time. Even if an attacker manages to control more than 50% of Bitcoin's computing power to perform a so-called 51% attack (or majority attack), the underlying protocol will quickly update in response to the attack.