A denial-of-service attack is one of the simplest ways for an attacker to take a business offline. When your website, online service, or critical system becomes unavailable, the impact is immediate. Revenue stops. Customers lose confidence. Operations stall. For many UK organisations, a successful denial of service attack is not just an inconvenience but a real operational and reputational threat.
At Amicis Group, we help organisations build resilience so they can continue operating even when under pressure. Denial of service attacks remain common but preventable with the right preparation, monitoring, and response capability.
What is a denial-of-service attack?
A denial-of-service attack (DoS) is an attempt to overwhelm a system so that legitimate users cannot access it. The attacker floods a website, application, or network with more traffic or requests than it can handle. When the service reaches its capacity, it slows down or becomes unavailable.
There are two primary forms:
Flood attacks: The attacker sends excessive traffic to exhaust bandwidth, memory, or processing power.
Crash attacks: Malformed or malicious packets trigger a failure in software or network components, causing a shutdown.
Unlike many other cyber threats, denial of service attacks usually aims to disrupt rather than steal data. They can still expose weaknesses, interrupt service delivery, and create opportunities for attackers to pivot into more serious activity.
What is a distributed denial-of-service attack?
A distributed denial of service attack (DDoS) uses multiple systems at the same time to target a single victim. Instead of one device sending excessive traffic, thousands of compromised machines across the world participate simultaneously.
This makes DDoS attacks:
- More powerful, due to massive, combined traffic volumes
- Harder to trace, because the traffic originates from many locations
- Difficult to block, as shutting down one device does not stop the attack
Most DDoS attacks rely on botnets. These are networks of computers or smart devices hijacked through malware. The owners are rarely aware their devices are being used for criminal activity.
DDoS attacks can be purchased cheaply on dark web marketplaces, making them accessible to inexperienced attackers as well as organised groups.
Why attackers carry out denial of service attacks
Attackers use denial of service attacks for several reasons, including:
- Financial gain: Criminals use DDoS threats to extort businesses. Paying does not guarantee the attack will stop or that it will not return.
- Political or ideological motives: Activists and state linked groups use DDoS to silence opposing views or disrupt organisations they disagree with.
- Cover for another attack: A denial-of-service attack may distract IT teams while attackers attempt credential theft, compromise email accounts, or deploy ransomware elsewhere.
- Misconfiguration or error: Not all outages are malicious. Overloaded servers, poor capacity planning, or software failures can produce self-inflicted denial of service conditions.
Understanding the motivation behind an attack is key to shaping the response.
Why a denial-of-service attack is difficult to stop
Stopping a DDoS attack is challenging because:
- The attack may involve tens of thousands of IP addresses
- Traffic looks normal until volume becomes extreme
- Attackers can switch tactics mid attack
- Filtering legitimate traffic from malicious traffic is complex
- Many attacks are short and repeated, making defence difficult without automation
Modern attacks also combine multiple methods at once. For example, network floods, application layer requests, and encrypted traffic may all be used together to bypass basic filtering.
This is why proactive measures and real time detection are essential.
Fake traffic and blended attacks
Attackers increasingly hide denial of service traffic within legitimate looking traffic streams. Some attacks mimic user behaviour, send requests intermittently, or target specific application functions.
Blended attacks may also combine:
- Denial of service traffic
- Brute force login attempts
- Credential stuffing
- Exploitation of unpatched vulnerabilities
This multi layered approach is designed to distract, overwhelm, and then breach.
How to prevent a denial of service or distributed denial of service attack
Preventing a DoS or DDoS attack requires infrastructure that can absorb, deflect, or filter hostile traffic before it reaches your environment. Endpoint protection, MDR, or traditional firewalls are not designed for large-scale volumetric attacks. Effective defence relies on a combination of cloud-based mitigation, network architecture, and real-time traffic analysis.
Attack surface reduction
Reducing what the public Internet can reach minimises opportunities for disruption. This includes:
- Blocking unused ports and legacy protocols
- Restricting access by region or network segment
- Placing origin servers behind a Cloudflare reverse proxy
- Removing direct exposure of applications to the Internet
This ensures only essential traffic reaches the edge.
Anycast network diffusion
DDoS resilience depends on distributing traffic across a global network. Cloudflare’s Anycast architecture spreads incoming traffic across a worldwide footprint, preventing volumetric attacks from overwhelming any single location.
Always-on cloud DDoS mitigation
Cloud-based mitigation absorbs and filters malicious traffic before it reaches your infrastructure. With Cloudflare, automated L3–L7 protection:
- Detects anomalies within seconds
- Drops malicious packets at the edge
- Blocks protocol abuse, amplification attempts, and spoofed traffic
- Prevents application-layer floods from overwhelming your origin
This provides scale that on-premises infrastructure cannot achieve.
Real-time threat monitoring
Monitoring traffic patterns in real time enables early identification of:
- Rapid traffic spikes
- Application-layer anomalies
- Repeated or malformed requests
- High-volume flows from botnets or proxies
Cloudflare provides live analytics and automatic enforcement at the network edge.
Rate limiting and request filtering
Rate limiting is essential to prevent high-frequency bursts of traffic from overwhelming web servers. This includes:
- Per-IP request limits
- Adaptive thresholds
- Burst control
- Behavioural-based rules
Used correctly, rate limiting neutralises many application-layer attacks.
Caching and content offload
Caching reduces demand on origin servers during high traffic periods by serving static assets from distributed nodes. A CDN such as Cloudflare reduces the volume of traffic that hits the origin, making it harder for attackers to trigger outages.
Web Application Firewall tuning
A modern WAF helps block malicious application-layer activity, including:
- Layer 7 floods
- Automated scraping
- Manipulated headers
- Attack tools such as LOIC or Slowloris
Custom rule-sets improve protection for healthcare, e-commerce, finance, and high-risk environments.
Protecting against DoS and DDoS attacks with Amicis Group
Amicis Group provides end-to-end support for organisations that need strong, modern DDoS resilience. Through our Cloudflare partnership, we deliver:
- Always-on DDoS protection at the network edge
- Global Anycast defence
- L3–L7 filtering and adaptive mitigation
- WAF configuration and tuning
- Traffic analysis and incident response
- Strategic attack surface reduction
- Architecture reviews for Internet-facing services
This sits alongside our CyberGuard and SOC services, which provide monitoring, threat detection, and operational resilience but are not standalone DDoS mitigation tools.
Call us today on 0333 305 5348 or use our Contact Us page to discuss how you can further protect your business.
You may also be interested in our Cloud Protection page.
