Denial of Service Attacks
By Malcolm McDonald Founder, Editor-in-ChiefAuthor of Grokking Web Application Security
Sometimes attackers don't need to hack your website, they just want to make it unavailable to others.
- Prevalence
- Occasional
- Exploitability
- Moderate
- Impact
- Harmful
What is a denial of service attack?
A denial of service (DoS) attack is an availability attack in which an attacker floods a website with traffic or expensive requests until it runs out of resources and cannot serve legitimate users. When the traffic comes from many machines at once, typically a botnet, it is called a distributed denial of service (DDoS) attack.
What you'll learn
- How SYN floods, slow reads and reflected attacks exhaust a server
- What makes a distributed denial of service attack harder to block
- How traffic filtering, protection services and scalable design keep a site online
This lesson includes
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Denial of Service Attacks lab
Tour the ways attackers knock a site offline, from SYN floods and slow reads to reflected attacks and botnet-driven distributed attacks. Midway through, write an IP netmask that blocks the attacking traffic while keeping real users connected.
-
How to prevent Denial of Service Attacks
The prevention guide covers two approaches:
- Use Commercial Protection Services
- Build Your Site to Scale
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Denial of Service Attacks quiz
Three questions. Passing marks the lesson complete.
Sources
- Famous DDoS attacks: The largest DDoS attacks of all time Cloudflare
- Defending against distributed denial of service (DDoS) attacks Canadian Centre for Cyber Security
- Application Level Denial of Service – A Comprehensive Guide Netsparker
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