DNS Floods

A DNS flood is a type of Denial of Service (DoS) attack where attackers overwhelm a target's DNS servers with a flood of DNS requests. These requests can be either valid or malformed, and are designed to consume server resources, rendering the DNS service unresponsive to legitimate traffic. This disrupts domain resolution, essentially making websites and online services inaccessible.

Impact

DNS floods can cripple online services by blocking domain name resolution, which is a core function of internet connectivity. Users attempting to visit a website under attack may see connection timeouts or DNS errors. For businesses, this can mean lost revenue, reduced user trust, and brand damage. Moreover, if DNS services are outsourced, costs may rise due to excess bandwidth usage or mitigation services.

Discoverability

DNS flood attacks are relatively easy to discover once the attack is underway due to a sharp spike in DNS traffic, especially from unusual sources or in very high volume. Network monitoring tools can detect anomalies in DNS query patterns. However, distinguishing an attack from a legitimate traffic spike may require deep packet inspection or advanced behavioral analysis.

Tools

• LOIC (Low Orbit Ion Cannon): Though originally designed for HTTP flooding, LOIC can be configured to perform DNS floods with custom payloads.
• Hping3: A packet crafting tool that allows attackers to forge DNS packets and flood a DNS server with customized traffic.
• Metasploit Framework: Includes modules for generating custom DNS request floods as part of advanced DoS testing.

Protection

• Rate Limiting: Restricting the number of requests per IP or network range can prevent overwhelming bursts of DNS queries.
• Anycast DNS: Distributes DNS traffic across multiple nodes worldwide, increasing resilience to flood attacks.
• DNS Firewall Services: Services like Cloudflare or Akamai provide DNS-layer DDoS protection that can absorb and deflect large-scale floods.
• Monitoring and Anomaly Detection: Implementing continuous traffic monitoring to detect and respond to unusual DNS traffic patterns early.