Road to CEH Masters Week 10: Denial-of-Service

Understanding Denial-of-Service (DoS) Attacks: A Comprehensive Guide

Denial-of-Service (DoS) attacks are a prevalent threat in cybersecurity, designed to disrupt the availability of services on a target system or network. This module explores the intricacies of DoS and Distributed Denial-of-Service (DDoS) attacks, their mechanisms, and mitigation strategies.

What is a DoS Attack?

A DoS attack aims to make a system’s resources unavailable to legitimate users by overwhelming it with excessive traffic or service requests. This can result in significant performance degradation or complete system failure. Common forms of DoS attacks include:

• Flooding Attacks: Overwhelming the target system with more traffic than it can handle.
• Service Exploitation: Crashing services by interacting with them unexpectedly or sending corrupt packets.
• Resource Consumption: Utilizing all available bandwidth, disk space, CPU time, or other resources to incapacitate the system.

DoS attacks can significantly impact an organization’s operations by consuming resources and potentially causing the loss of critical services, although they do not typically result in data theft.

DDoS Attacks: A Broader Threat

DDoS attacks are a more sophisticated form of DoS attacks, involving multiple compromised computers (botnets) to launch coordinated attacks on a single target. These attacks are harder to trace and can quickly overwhelm even the largest networks due to the combined bandwidth of multiple attacking systems. Key aspects of DDoS attacks include:

• Botnets: Networks of infected computers controlled by attackers to execute DDoS attacks, generate spam, and more.
• Attack Mechanisms: Use of zombie agents and command and control servers to flood the target system with fake requests.
• Impact: Loss of goodwill, financial losses, and disabled networks.

Notable Attack Types

1. TCP Sack Panic Attack: Exploits vulnerabilities in Linux systems’ TCP Selective Acknowledgment (SACK) to cause kernel panic and DoS.
2. Distributed Reflection DoS (DRDoS): Involves multiple intermediary machines reflecting attack traffic to the target, exploiting the TCP three-way handshake process.
3. Ransom DDoS (RDDoS): Attackers threaten to launch a DDoS attack unless a ransom is paid, often demonstrating their capabilities with a sample attack.

Case Study: Microsoft Azure DDoS Attack

In August 2021, Microsoft Azure experienced a 2.4 Tbps DDoS attack, significantly impacting service availability for over 10 minutes. This UDP reflection attack originated from spoofed IP addresses and targeted Azure’s infrastructure, demonstrating the scale and potential disruption of modern DDoS attacks. Microsoft’s DDoS protection platform eventually mitigated the attack by monitoring and responding to the traffic anomaly.

Mitigation Strategies

To protect against DoS and DDoS attacks, organizations should implement robust defense mechanisms, including:

• Vulnerability Patching: Regular updates and patches to fix known vulnerabilities.
• Firewalls and Filtering: Blocking malicious traffic at the network perimeter.
• DDoS Protection Services: Leveraging services that provide continuous monitoring and automatic mitigation of DDoS attacks.
• Incident Response Plans: Developing and testing response strategies to quickly address and mitigate attacks when they occur.

Tools Used in DoS/DDoS Attacks

Various tools are available for launching DoS and DDoS attacks, some of which include:

• High Orbit Ion Cannon (HOIC): Capable of targeting multiple URLs simultaneously with high-speed HTTP flooding.
• Low Orbit Ion Cannon (LOIC): A popular tool for stress testing and performing application-based DoS attacks.
• Mobile Tools: Android applications like LOIC and AnDOSid that enable attackers to perform DoS attacks from mobile devices.

By understanding the mechanisms, impacts, and mitigation strategies for DoS and DDoS attacks, organizations can better prepare and defend against these disruptive threats. Implementing comprehensive security measures and staying informed about emerging attack techniques are critical steps in maintaining robust cybersecurity defenses.

With my study notes I have create a set of 9 flashcards that can be accessed here: Module 10 – Flash Cards

I have also created this visual Mind map: Module 10 – Mindmap

If you have any questions or any feedback feel free to comment or leave a message on the homepage as that will send directly to me!

Thanks for reading!