Denial of Service (DoS) attacks
A Denial of Service (DoS) attack occurs when a system is flooded with excessive traffic or requests, preventing legitimate users from accessing services. This overwhelms the system’s resources so it cannot respond normally.
Symptoms
- Slow performance when accessing systems
- Websites or services become unavailable
- Requests take a long time or fail completely
Effects
- Disruption to users trying to access services
- Businesses experience downtime
- Loss of user trust and reliability
Costs
- Lost revenue due to service unavailability
- Time and labour required to fix the issue
- Additional costs to improve security
Types of fault
- Bandwidth consumption
- Network is flooded with traffic
- Legitimate data cannot get through
- Resource starvation
- CPU or memory becomes overloaded
- System cannot process requests
- DNS attacks
- The Domain Name System (DNS) is responsible for converting website names (e.g. google.com) into IP addresses that computers use
- In a DNS DoS attack, attackers overwhelm DNS servers with large numbers of requests
- This prevents the DNS server from responding to legitimate requests
- As a result, users cannot resolve website names into IP addresses
- This means:
- Websites cannot be found or loaded
- Users may see errors even though the website itself is still running
- Key idea:
The attack does not target the website directly — it targets the system that helps users find the website, making it inaccessible.
Reasons for attacks
- Financial
- Extortion or causing financial loss
- Political
- Hacktivism (cyber attacks to promote a political or social cause) or protest
- Personal
- Revenge or disruption