Security – DNS

DNS (Domain Name System) is an essential part of the internet’s infrastructure that translates human-friendly domain names to IP addresses. However, as with any essential piece of infrastructure, it is a popular target for bad actors or cybercriminals. Below are some ways bad actors exploit DNS:

  • DNS Hijacking: Attackers redirect queries to a malicious DNS server. For example, if a user tries to visit a banking website, the corrupted DNS server sends the user to a phishing site instead, which might look identical to the real site. The user then inadvertently gives their login information to the attacker.
  • DNS Tunneling: Attackers can encapsulate non-DNS traffic in DNS queries and responses, essentially using the DNS as a covert communication channel to bypass firewalls and data exfiltration.
  • DNS Amplification and Reflection Attacks: Attackers send a small query to a DNS server but forge the return IP address to be the victim’s IP. The DNS server then sends a large response to the victim’s IP, overwhelming the victim’s network with traffic (DDoS attack).
  • Subdomain Attacks: Attackers continually make DNS requests for non-existent subdomains, causing the DNS server to become overwhelmed with trying to resolve these fake subdomains.
  • Cache Poisoning (DNS Spoofing): Attackers corrupt the DNS query process to return a false IP address, directing users to malicious websites.
  • Phantom Domain Attacks: Attackers set up phantom domains to exhaust DNS resolvers’ resources by forcing them to wait for responses from these nonexistent or slow-responding domains.

Here are some recommendations to prevent these types of attacks:

  • Use DNSSEC (DNS Security Extensions): This can help prevent cache poisoning and DNS spoofing attacks by providing DNS response authentication. However, it doesn’t protect against all types of DNS attacks.
  • Regularly Update and Patch DNS servers: This ensures that servers are protected from known vulnerabilities that attackers could exploit.
  • Enable DNS Query Monitoring and Logging: This can help you identify unusual patterns or spikes in DNS traffic, which could indicate a DNS attack. Many modern security information and event management (SIEM) solutions offer DNS log analysis.
  • Use DNS Firewalls and Intrusion Prevention Systems (IPS): These can help identify and block malicious DNS queries.
  • Block DNS requests to external DNS servers: By forcing all DNS queries to go through your internal DNS server, you can control and monitor DNS traffic more effectively.
  • Implement Rate Limiting: This can help protect against DDoS attacks by limiting the number of requests a server can accept within a certain timeframe.
  • Employ Threat Intelligence Tools: These tools can help identify malicious domains and prevent connections to them.
  • Regular Security Awareness Training: Many DNS attacks involve some form of social engineering. Regular training can ensure that employees know how to identify and avoid potential threats.
  • Use Redundant DNS servers: In case one server is compromised, the other one can continue to operate, reducing the overall risk of a successful attack.

Remember, it’s not a question of whether an attack will happen but when. Thus, enterprises need to develop a comprehensive and ongoing approach to DNS security.