DoS Attack

A DoS attack (Denial of Service) is a type of cyber attack where a malicious actor intentionally overwhelms a server, website, or network resource with a large number of requests, rendering it unavailable to regular users. The goal of such an attack is to “take down” the service, disrupt its operation, or completely block access to it.

What is a DoS Attack?

DoS (Denial of Service) translates to “denial of service.”
The attack aims to overload a server to the point where it can no longer handle legitimate requests.
This happens because the system is flooded with excessive requests, receives too many inquiries, or faces resource-intensive operations.

How Does a DoS Attack Work?

The essence of the attack is simple:

1. The attacker sends a large number of requests to the server.
2. The server tries to process them.
3. The load increases, and resources are exhausted.
4. The website slows down, freezes, or stops responding entirely.

The requests can include:

• Network packets
• HTTP requests
• Port requests
• Commands requiring high computational power.

Main Types of DoS Attacks

1. Flood Attacks
   Overwhelming the server with a large volume of packets—e.g., ICMP Flood, UDP Flood, SYN Flood.
2. Application-Level DoS
   Targeting specific services or website functions—e.g., repeatedly executing resource-intensive operations.
3. Logical Attacks
   Exploiting software, protocol, or configuration vulnerabilities.

How DoS Differs from DDoS

• DoS: The attack originates from a single device or a small number of sources.
• DDoS: The attack originates from thousands or millions of devices simultaneously (a botnet).
  DDoS is much harder to stop, though a DoS attack can still incapacitate a small server.

Signs of a DoS Attack

• Sudden slowdown of the website
• Website becomes inaccessible
• High CPU and memory usage on the server
• Traffic surge from a single source
• Error 503 (“Service Unavailable”)
• Unstable performance of all services

Why Attackers Launch DoS Attacks

Motivations can vary:

• Extortion attempts
• Competitive sabotage
• Protests or political motives
• Vulnerability testing
• Distraction before a hacking attempt

How to Protect Against DoS Attacks

1. Implement rate limiting
   Restrict the number of requests from a single IP address.
2. Use traffic filters
   Firewalls, IDS/IPS systems.
3. Configure CAPTCHA
   Often used to protect against automated requests.
4. Apply server-side restrictions
   Clean and limit request queues.
5. Migrate to protected hosting
   Use CDN services (e.g., Cloudflare, Akamai) or anti-DDoS solutions.
6. Monitor traffic
   Early detection of anomalies.

Example of a Simple DoS Attack (Explained Without Technical Details)
An attacker sends thousands of requests to a search page. The server attempts to process each request but runs out of resources—the search function “crashes,” followed by the entire website going down.

Summary

A DoS attack is an attempt to incapacitate a service by overwhelming it with excessive requests. It blocks user access, disrupts website functionality, and poses risks to business operations.