Glossary

Denial of Service

A Denial of Service (DOS) attack is a technique used by attackers to prevent legitimate users from accessing a website, application, data, or other services. This is commonly achieved by making multiple “false” requests to a web server or application. The number of these requests overloads the capacity of the targeted system, meaning it has no resources to serve legitimate users.

Terms related to Denial of Service: Distributed denial of service attack, DOS attack, attacker, malware, cybersecurity, exploit, botnet, load balancing, trojan horse, reverse proxy, application gateway

Denial of service attacks come in several forms, some of the most popular include:

  • Overwhelming the network with “fake” traffic that crowds out and prevents valid traffic from legitimate users.
  • Interrupting the transmission and receipt of data between two machines, thereby preventing access.
  • Disrupting services between specific individuals, machines, or systems.
  • Disrupting traffic protocols, networks, or sessions.

DOS attacks are often perpetrated using “botnets” — a collection of computers that have been infected with malware, like a Trojan Horse, allowing an attacker to remotely control them and to send spurious traffic to the service they are attacking.

DOS attacks can result in slow, inefficient or non-responsive services, interruption of network traffic, interference with legitimate connections, and more. For organizations that rely on their website or web applications, defending against DOS attacks should be a high priority.

Defenses against denial of service attacks include:

  • Web application firewalls to identify and block specific traffic or traffic patterns.
  • Reverse proxies and application gateways to filter, reject, or redirect traffic.
  • Load balancing services that distribute traffic across multiple web servers so that one server does not become overwhelmed.

Denial of Service Resources from Crossmatch