CEH v13: Denial-of-Service
Table of Contents
Click Here to Return To the Certified Ethical Hacker (CEH v13) Course Page
Denial-of-Service attacks disrupt availability in the EC-Council CEH v13 course. This module covers DoS and DDoS techniques, attack categories, botnets, and the defenses that absorb them. Run flooding tools only against isolated lab systems you own, never against live targets.
A denial-of-service attack overwhelms a system so legitimate users lose access. It targets the availability pillar of the CIA triad rather than stealing data.
DoS vs. DDoS
The difference is the number of sources.
| Attack | Sources | Harder to block |
|---|---|---|
| DoS | One host | No |
| DDoS | Many hosts (a botnet) | Yes |
A botnet is a network of compromised devices a command-and-control server directs to flood a target at once.
Attack Categories
You group attacks by the layer they hit.
- Volumetric attacks flood bandwidth (UDP floods, ICMP floods).
- Protocol attacks exhaust connection tables (SYN floods).
- Application-layer attacks exhaust server resources with valid-looking requests (HTTP floods).
Amplification and reflection make small requests produce huge responses. An attacker spoofs the victim’s IP, queries open DNS or NTP servers, and those servers blast large replies at the victim.
Tools in the Lab
| Tool | Use |
|---|---|
| hping3 | Crafts custom flood packets |
| LOIC / HOIC | Simple flooding utilities |
| Slowloris | Holds many slow connections open |
# Lab-only SYN flood simulation against an isolated host
sudo hping3 -S --flood -p 80 10.0.0.5
Defenses
You absorb and filter attack traffic with layered controls.
- Rate limiting caps requests per source.
- Scrubbing centers filter malicious traffic before it reaches you.
- Anycast spreads traffic across many data centers.
- A CDN absorbs volumetric load at the edge.
Defense works best upstream, because a flood that fills your link cannot be stopped at your firewall.
Next Steps
Take over live sessions in Session Hijacking . Revisit human attacks in Social Engineering . Return to the Certified Ethical Hacker (CEH v13) Course .
