denialofservice

Denial of service is a class of cyberattacks designed to make a system's services unavailable to legitimate users by exhausting or degrading essential resources such as bandwidth, processing power, or memory. The objective is to disrupt operations, degrade performance, or exhaust the target's assets, potentially affecting customers, partners, or users. A related form, distributed denial of service (DDoS), uses multiple compromised machines to coordinate an attack, making mitigation harder by increasing volume and distributing the source of traffic.

Attackers employ several high-level categories of techniques. Volumetric attacks aim to saturate the target's bandwidth with large volumes of traffic. Protocol attacks exploit weaknesses in network protocol implementations or intermediaries to consume connection state or processing capacity. Application-layer attacks target specific features or endpoints of an application, exhausting resources with seemingly legitimate requests. Some attacks use amplification or reflection to generate larger traffic with minimal own traffic, often abusing third-party services. The effectiveness of a DoS depends on the target's capacity, the attack's scale, and defensive measures.

Defenses emphasize redundancy and resilience. Traffic can be absorbed or redirected using load balancing, content delivery networks, and scrubbing centers. Rate limiting, firewall rules, and intrusion detection systems help identify and filter malicious traffic. Network design choices such as anycast, distributed infrastructure, and excess capacity improve tolerance. Organizations typically plan incident response, monitor for sudden traffic anomalies, and coordinate with service providers to mitigate attacks.

Legal and ethical considerations: unauthorized DoS attacks are illegal in many jurisdictions. Penetration testing and stress testing should be conducted only with explicit permission and appropriate safeguards.