Not all cyberattacks aim to steal data. Some attacks are designed to make systems unusable. In IB Computer Science, this type of attack is known as a Denial of Service (DoS) attack. When such attacks are launched on a larger scale using many systems, they are called Distributed Denial of Service (DDoS) attacks.
IB examiners expect students to explain how these attacks work, why they are effective, and their impact on availability.
What Is a Denial of Service (DoS) Attack?
A Denial of Service (DoS) attack occurs when:
- A system is overwhelmed with requests
- Legitimate users are unable to access services
The goal of a DoS attack is:
- To exhaust system resources
- To make a service unavailable
In IB terms, DoS attacks target availability, not confidentiality or integrity.
How DoS Attacks Work
DoS attacks work by:
- Flooding a system with traffic
- Consuming processing power, memory, or bandwidth
As a result:
- The system slows down
- Crashes
- Stops responding
Even well-secured systems can be affected because:
- The attack uses normal-looking requests
What Is a Distributed Denial of Service (DDoS) Attack?
A Distributed Denial of Service (DDoS) attack is an advanced form of DoS.
In a DDoS attack:
- Traffic comes from many different systems
- Attackers use a network of compromised devices
These compromised devices are often part of a:
- Botnet
DDoS attacks are harder to stop because:
- Traffic originates from many locations
Why DDoS Attacks Are More Dangerous
DDoS attacks are more dangerous because:
- They generate massive traffic volumes
- Blocking a single source is ineffective
- Attacks can last for long periods
Large organisations and public services are common targets because:
- Disruption causes significant damage
IB students should link DDoS attacks to scale and coordination.
Impact of DoS and DDoS Attacks
These attacks can cause:
- Website downtime
- Loss of revenue
- Reputational damage
- Service disruption
For critical systems such as:
- Banking platforms
- Government services
- Online education systems
availability is essential.
Why DoS and DDoS Are Hard to Prevent
DoS and DDoS attacks are difficult to prevent because:
- Attack traffic resembles legitimate traffic
- Attackers use many devices
- Systems must remain publicly accessible
Blocking all traffic is not an option, as it would deny service to real users.
Mitigating DoS and DDoS Attacks
Common mitigation strategies include:
- Traffic filtering
- Rate limiting
- Load balancing
- Use of specialised DDoS protection services
IB students should understand that:
- Mitigation reduces impact
- Attacks may not be fully prevented
DoS Attacks and Risk Assessment
DoS and DDoS attacks are:
- High-impact threats
- Especially risky for online services
Risk assessments often prioritise:
- Availability protection
- Redundancy and resilience
Common Student Mistakes
Students often:
- Confuse DoS with hacking or data theft
- Ignore availability
- Forget distributed nature of DDoS
- Describe attacks too vaguely
Clear explanation of intent and impact earns marks.
How This Appears in IB Exams
IB questions may ask students to:
- Define DoS or DDoS attacks
- Compare the two
- Explain their impact on systems
- Suggest mitigation strategies
Explanation matters more than technical detail.
Final Thoughts
Denial of Service attacks aim to make systems unavailable by overwhelming resources, while Distributed Denial of Service attacks achieve the same goal using many compromised devices. These attacks target availability and can disrupt even secure systems.
Understanding DoS and DDoS attacks allows IB Computer Science students to explain why availability is a critical part of system security — exactly what examiners expect.
