Denial of Service (DoS) is a type of cyber attack that involves flooding a network or website with traffic or requests, often causing the system to crash or become unavailable to users.

What is DoS attack?

DoS attack (Denial of Service) is a type of cyberattack where an attacker floods a target—such as a server, website, or network—with excessive traffic or requests. The goal is to overload system resources, making the service unavailable to legitimate users. The effects can range from slowdowns to complete outages.

How DoS attack appears in practice

Common real-world scenarios:

• A company website suddenly goes offline, even though the hosting usually handles normal traffic.
• An online customer support system becomes unresponsive due to traffic overload.
• The internal company network is heavily slowed, disrupting employee productivity.
• An e-commerce site can’t process orders, despite it not being a high-traffic period.
• A key IT system goes down for hours without any apparent hardware failure.

These scenarios often occur without warning and can lead to financial losses, customer dissatisfaction, or even legal issues, due to SLA violations or compliance failures.

DoS (Denial of Service) vs. DDoS and Other Terms

• DoS (Denial of Service) – The attack originates from a single source (e.g., one device or IP address).
• DDoS (Distributed Denial of Service) – The attack comes from multiple sources simultaneously, often using a botnet of infected devices.
• Brute-force attack – A different threat aimed at cracking passwords through repeated login attempts.

Main distinction: DoS is simpler and easier to detect. DDoS is larger in scale, harder to defend against, and often requires advanced mitigation strategies.

How to prepare for DoS attack and assess the risk

Recommended actions for businesses:

1. Identify mission-critical systems — websites, APIs, email services.
2. Implement network-level protections such as firewalls, intrusion detection (IDS), and prevention systems (IPS).
3. Use cloud platforms that offer built-in DoS/DDoS protection.
4. Monitor network traffic for anomalies like sudden spikes, which can be early warning signs.
5. Create an incident response plan outlining how to act, who is responsible, and how to inform customers.
6. Consider web protection services like WAFs (Web Application Firewalls) or anti-DDoS platforms such as Cloudflare, Akamai, or AWS Shield.

A DoS attack may be technically simple but can be devastating if unprepared. Even short outages can result in serious disruptions. Preventive planning is far less costly than reacting after the damage is done.