DDoS Protection: How to Protect Your Server from Attacks

Distributed Denial of Service (DDoS) attacks are one of the most common and disruptive threats facing online businesses today. Understanding how these attacks work and how to protect against them is essential for anyone operating server infrastructure.

What is a DDoS Attack?

A DDoS attack attempts to overwhelm your server or network with traffic from multiple sources, making your services unavailable to legitimate users. Unlike simple DoS attacks from a single source, DDoS attacks use distributed botnets—networks of compromised computers—to generate massive amounts of malicious traffic.

Modern DDoS attacks can generate hundreds of gigabits or even terabits of traffic per second, far exceeding what any single server can handle. Without proper protection, even a modest attack can take down your services.

Types of DDoS Attacks

Volume-Based Attacks

These attacks aim to saturate your network bandwidth with massive amounts of traffic:

• UDP Floods: Sends large volumes of UDP packets to random ports, forcing the server to check for applications and respond with ICMP "unreachable" packets
• ICMP Floods: Overwhelms the target with ICMP Echo Request (ping) packets
• Amplification Attacks: Exploits protocols like DNS, NTP, or memcached to amplify small requests into large responses directed at the target

Protocol Attacks

These exploit weaknesses in network protocols to exhaust server resources:

• SYN Floods: Exploits the TCP handshake by sending many SYN requests without completing the connection, exhausting server connection tables
• Ping of Death: Sends malformed or oversized packets that crash the target system
• Smurf Attack: Uses IP spoofing and ICMP to flood the target network

Application Layer Attacks

The most sophisticated attacks target specific applications:

• HTTP Floods: Sends seemingly legitimate HTTP requests to overwhelm web servers
• Slowloris: Opens many connections and sends partial requests, keeping connections open and exhausting server resources
• Application-specific attacks: Target vulnerabilities in specific software like WordPress, API endpoints, or login pages

Impact of DDoS Attacks

DDoS attacks cause significant damage beyond simple downtime:

• Revenue loss: E-commerce sites lose sales; SaaS companies lose billable hours
• Reputation damage: Customers lose trust in unreliable services
• Operational costs: Staff time spent responding to attacks
• Ransom demands: Attackers often demand payment to stop attacks
• Distraction: DDoS may cover other attacks like data breaches

DDoS Protection Strategies

1. Network-Level Protection

The first line of defense filters malicious traffic before it reaches your server:

• Upstream filtering: Your hosting provider filters attacks at the network edge
• BGP blackholing: Routes attack traffic to null during volumetric attacks
• Scrubbing centers: Traffic passes through cleaning facilities that remove malicious packets

2. Server-Level Hardening

Configure your server to better handle attack traffic:

• Increase connection limits: Tune kernel parameters likenet.core.somaxconn and net.ipv4.tcp_max_syn_backlog
• Enable SYN cookies: Prevents SYN flood attacks from exhausting connection tables
• Configure timeouts: Reduce keepalive timeouts to free resources faster
• Rate limiting: Use iptables or nftables to limit connections per IP

3. Application-Level Protection

Protect your applications from layer 7 attacks:

• Web Application Firewall (WAF): Filters malicious HTTP requests
• Rate limiting: Limit requests per IP at the application level
• CAPTCHA challenges: Verify human users during suspected attacks
• Caching: Serve cached content to reduce origin server load

4. CDN and Proxy Services

Content Delivery Networks can absorb attack traffic across their distributed infrastructure:

• Distribute traffic across multiple points of presence
• Hide your origin server IP address
• Provide additional caching and WAF capabilities
• Offer specialized DDoS mitigation features

What to Look for in DDoS Protection

Capacity

Ensure your provider can handle attacks larger than current threat levels. Look for providers advertising protection capacity of at least 1 Tbps for volumetric attacks.

Mitigation Speed

How quickly does protection activate? The best solutions offer always-on protection with instant mitigation. Others may take seconds to minutes to detect and mitigate attacks.

Attack Types Covered

Ensure protection covers all three attack categories: volumetric, protocol, and application layer. Some basic protections only handle volumetric attacks.

Legitimate Traffic Handling

Poor DDoS protection can block legitimate users. Look for providers with low false positive rates and intelligent traffic analysis that distinguishes real users from attackers.

Reporting and Visibility

Good providers offer dashboards showing attack traffic, mitigation actions, and historical data. This helps you understand your threat landscape.

During an Attack: Response Checklist

• Verify it's a DDoS: Rule out other causes like legitimate traffic spikes or server issues
• Contact your provider: Alert them immediately so they can activate additional mitigation
• Document the attack: Record traffic patterns, timing, and impact for post-incident analysis
• Enable additional protections: Activate any available WAF rules or rate limits
• Communicate with stakeholders: Inform customers and management about the situation
• Don't pay ransoms: Payment encourages future attacks and doesn't guarantee they'll stop

Prevention Best Practices

• Choose hosting with built-in protection: Many quality providers include DDoS mitigation
• Keep origin IP hidden: Use CDN/proxy services and never expose your real server IP
• Have a response plan: Document procedures before an attack happens
• Monitor traffic patterns: Establish baselines so you can quickly identify anomalies
• Test your defenses: Conduct authorized stress tests to verify protection works

Conclusion

DDoS protection is no longer optional for any online business. The frequency and sophistication of attacks continue to increase, making robust protection essential. Choose a hosting provider with strong built-in DDoS mitigation, implement server and application-level hardening, and have a response plan ready.

At Packet25, all dedicated servers include DDoS protection as standard, with network-level filtering capable of absorbing large-scale attacks before they reach your server.