Slow Server Attacks: Prevention

TL;DR

Yes, attackers can slow down your server without getting full control (compromising it). This is often done through denial-of-service attacks or by exploiting resource limitations. We’ll cover how to identify these attacks and steps you can take to protect yourself.

Understanding Slow Server Attacks

These attacks don’t usually involve stealing data, but they can make your website unavailable or very slow for legitimate users. Common types include:

• Denial-of-Service (DoS) / Distributed Denial-of-Service (DDoS): Flooding your server with traffic it can’t handle.
• Slowloris: Sending partial HTTP requests to keep connections open, exhausting resources.
• HTTP Flood: Overwhelming the web server with legitimate-looking HTTP requests.
• Resource Exhaustion Attacks: Exploiting bugs or misconfigurations to consume CPU, memory, or disk I/O.

Steps to Protect Your Server

1. Monitor Server Resources: Regularly check your server’s CPU usage, memory consumption, network traffic, and disk I/O.
   • Use tools like top (Linux) or Task Manager (Windows).
   • Consider using a monitoring service like Nagios, Zabbix, or New Relic.
2. Implement Rate Limiting: Limit the number of requests from a single IP address within a specific timeframe.

   # Example Nginx rate limiting configuration
   limit_req_zone $binary_remote_addr zone=mylimit:10m rate=5r/s;
   
   server {
     ...
     location / {
       limit_req zone=mylimit burst=20 nodelay;
       ...
     }
   }

3. Use a Web Application Firewall (WAF): A WAF filters malicious traffic before it reaches your server.
   • Popular options include Cloudflare, Sucuri, and ModSecurity.
   • Configure the WAF to block common attack patterns.
4. Keep Software Updated: Regularly update your operating system, web server software (e.g., Apache, Nginx), and any applications running on your server.
   • Updates often include security patches that address vulnerabilities exploited by attackers.
   • sudo apt update && sudo apt upgrade (Debian/Ubuntu) or yum update (CentOS/RHEL).
5. Configure Connection Limits: Limit the maximum number of concurrent connections to your server.

   # Example Apache connection limits configuration
   MaxRequestWorkers 150
   MinSpareThreads 25
   MaxSpareThreads 75

6. Enable Keep-Alive Timeout: Reduce the keep-alive timeout to free up resources more quickly.
   • Long keep-alive times can allow attackers to maintain many open connections.
7. Use a Content Delivery Network (CDN): A CDN distributes your website’s content across multiple servers, reducing the load on your origin server.
   • Cloudflare and Akamai are popular CDN providers.
8. Implement DDoS Protection Services: Specialized services can mitigate large-scale DDoS attacks.
   • These services often use techniques like traffic scrubbing and anycast routing.
9. Review Server Logs: Regularly analyze your server logs for suspicious activity, such as unusual request patterns or errors.
   • Look for repeated requests from the same IP address or requests that are causing performance issues.

Further Considerations

If you suspect a DoS/DDoS attack, contact your hosting provider immediately. They may be able to provide additional assistance and mitigation measures.