What Are Denial of Service (DoS) Attacks?

Denial-of-service (DoS) attacks are a type of malicious cyberattack with the sole purpose of disabling a targeted device or service. By overloading services or machines with data, the receiving side becomes overwhelmed and services are rendered useless. This can be done in multiple different ways and are all threats to a business without proper protection and security.

What Are Denial of Service (DoS) Attacks?

Types of DoS Attacks

Buffer Overflow Attacks

Buffer overflow attacks are the most common in which the attack targets disk–drive space, a computer's memory or the central processing unit. This results in crashes, sluggish interaction, and possibly the infamous “blue screen of death”. 

Flood Attacks

Flood attacks are another type of overloading but with the use of network packets consisting of control information and user data. By relaying these packets over and over through the use of the sender's bandwidth, it can overwhelm the target and deny service. 

Flood attacks have two different variations: ICMP and SYN. ICMP floods will attack using a fake variation of the previously mentioned packets to ping every computer on a targeted network rather than only one machine. This triggers the network and the effect is amplified as the entire network joins in what is known as the ‘ping of death”. SYN attacks send requests to a targeted server but that request is never met. As more and more requests attempt to “connect” it leaves no connections left for legitimate users of the system to use. 

Distributed Denial-of-Service (DDoS) Attacks

Distributed denial-of-service, or DDoS, utilizes many devices to spring an attack. The previously mentioned attacks usually stem from one device but a DDoS will use dozens of computers to overload a system, often from a botnet. A botnet refers to a group of devices contaminated with malware and given access to a malicious host who can order the group to attack a system. 


Denial-of-service attacks can often be directly attributed to a failed email protection system. For example, email-bombs are a form of DoS attacks that can be initiated from botnets for mass mailing or when an email with a malicious attachment or link is interacted with. This can trigger an effect that downloads terabytes of information to a system rendering it useless. Email security is as important as ever, and any business is at risk without effective supplementary email protection in place and the implementation of email security best practices.

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