A Denial-of-Service (DoS) attack is a cyber attack aimed at disrupting the normal functioning of a targeted system, server, or network resource, rendering it unavailable to its intended users. The primary purpose of a DoS attack is to deny access to online services or resources, causing inconvenience and potential financial or reputational damage to the target organization.
DoS attacks are typically carried out by overwhelming the targeted system with a massive volume of traffic or by exploiting its vulnerabilities to exhaust its resources. There are several methods for launching a DoS attack, including:
- Flood attacks: These involve sending an overwhelming number of requests or data packets to the target system, causing it to become overwhelmed and unable to process legitimate user requests. Examples of flood attacks include SYN flood, ICMP flood, and UDP flood attacks.
- Application-level attacks: These attacks target specific application vulnerabilities or weaknesses in server or application software. Examples include Slowloris and HTTP flood attacks.
- Resource exhaustion attacks: These attacks aim to deplete specific resources on the target system, such as memory, processing power, or bandwidth. An example is the NTP amplification attack, which exploits the Network Time Protocol to generate massive amounts of traffic.
A variant of the DoS attack is the Distributed Denial-of-Service (DDoS) attack, in which multiple compromised systems, often referred to as a botnet, are used to flood the target system with traffic. DDoS attacks are more challenging to defend against, as the attack traffic originates from multiple sources, making it difficult to identify and block the source.
Defending against DoS and DDoS attacks typically involves a combination of security measures, such as firewalls, intrusion detection systems, traffic filtering, and rate limiting. In addition, organizations can employ redundancy, load balancing, and content distribution networks to distribute the load and minimize the impact of an attack. Collaboration with Internet Service Providers (ISPs) and other security services can also help mitigate the effects of DoS attacks.
- Firewall - A network security system often used to mitigate the impact of DoS and DDoS attacks.
- Intrusion Detection System (IDS) - A device or software application for monitoring and reporting security breaches, which may include DoS attacks.
- TCP/IP (Transmission Control Protocol/Internet Protocol) - The foundational suite of protocols for the Internet, and a common vector for DoS attacks.
- Network Security - The broader discipline within which DoS protection measures fall.
- Cyber Security - The general field concerned with protecting systems, networks, and programs from digital attacks, including DoS.
- Secure Sockets Layer (SSL) - A cryptographic protocol for securing data transmission, relevant because SSL stripping can be part of some DoS attacks.