According to the Cybersecurity and Infrastructure Security Agency, “a denial-of-service (DoS) attack occurs when legitimate users are unable to access information systems, devices, or other network resources due to the actions of a malicious cyber threat actor” (CISA). It is often carried out by flooding a network server with traffic until it becomes unresponsive or crashes. This renders services such as emails and websites inaccessible to legitimate users (CISA). A Distributed Denial of Service Attack (DDoS) is identical to a DoS attack, just on a larger scale. It utilizes several machines to flood a targeted resource, rendering the attack more harmful and harder to track down. DDoS, as well as DoS attacks, are the most common attacks on availability, which is a type of cyberattack that impedes a user’s ability to access their information.
DDoS attacks can lead to significant consequences for businesses, such as a loss of revenue due to loss of sales and costs of recovery. Frequent DDoS attacks can cause reputational damage as they can affect customers’ trust in the company (Canadian Centre for CyberSecurity). Different types of DDoS attacks target different parts of a system. The overall impact depends on what is targeted and the duration of the attack (National Cyber Security Centre). The largest DDoS attack that happened recently occurred in October 2024. The attack primarily targeted an internet service provider in Eastern Asia. Web infrastructure and security company, Cloudflare, reported the attack reached 5.6 terabits per second and 666 million packets per second at its peak. The attack lasted about 80 seconds (Yoachimik and Pacheco).
Canadian Centre for CyberSecurity. “Defending against Distributed Denial of Service (DDoS) Attacks – ITSM.80.110.” Canadian Centre for Cyber Security, 9 Jan. 2024, www.cyber.gc.ca/en/guidance/defending-against-distributed-denial-service-ddos-attacks-itsm80110. Accessed 6 Apr. 2025.
CISA. “Understanding Denial-of-Service Attacks.” Cybersecurity and Infrastructure Security Agency, CISA, 1 Feb. 2021, www.cisa.gov/news-events/news/understanding-denial-service-attacks. Accessed 5 Apr. 2025.
National Cyber Security Centre. “Denial of Service (DoS) Guidance.” National Cyber Security Centre, 25 Mar. 2024, www.ncsc.gov.uk/collection/denial-service-dos-guidance-collection. Accessed 6 Apr. 2025.
Yoachimik, Omer, and Jorge Pacheco. “Record-Breaking 5.6 Tbps DDoS Attack and Global DDoS Trends for 2024 Q4.” The Cloudflare Blog, 21 Jan. 2025, blog.cloudflare.com/ddos-threat-report-for-2024-q4/. Accessed 6 Apr. 2025.