DNS Attacks

DNS Attacks
DNS Attacks

In this article we will talk about DNS Attacks, and in previous article we already discussed about Viruses and Trojan Horses.

DNS Attacks

The Domain Name Service (DNS) protocol defines an automated service that matches resource names, such as www.cisco.com, with the required numeric network address, such as the IPv4 or IPv6 address. It includes the format for queries, responses, and data and uses resource records (RR) to identify the type of DNS response.

Securing DNS is often overlooked. However, it is crucial to the operation of a network and should be secured accordingly.

DNS attacks include the following:

  • DNS open resolver attacks
  • DNS stealth attacks
  • DNS domain shadowing attacks
  • DNS tunneling attacks

DNS Open Resolver Attacks

Many organizations use the services of publicly open DNS servers such as GoogleDNS ( to provide responses to queries. This type of DNS server is called an open resolver. A DNS open resolver answers queries from clients outside of its administrative domain. DNS open resolvers are vulnerable to multiple malicious activities described in the table.

DNS Resolver VulnerabilitiesDescription
DNS cache poisoning attacksThreat actors send spoofed, falsified record resource (RR) information to a DNS resolver to redirect users from legitimate sites to malicious sites. DNS cache poisoning attacks can all be used to inform the DNS resolver to use a malicious name server that is providing RR information for malicious activities.
DNS amplification and reflection attacksThreat actors use DoS or DDoS attacks on DNS open resolvers to increase the volume of attacks and to hide the true source of an attack. Threat actors send DNS messages to the open resolvers using the IP address of a target host. These attacks are possible because the open resolver will respond to queries from anyone asking a question.
DNS resource utilization attacksA DoS attack that consumes the resources of the DNS open resolvers. This DoS attack consumes all the available resources to negatively affect the operations of the DNS open resolver. The impact of this DoS attack may require the DNS open resolver to be rebooted or services to be stopped and restarted.
DNS Attacks Resolver

DNS Stealth Attacks

To hide their identity, threat actors also use the DNS stealth techniques described in the table to carry out their attacks.

DNS Stealth TechniquesDescription
Fast FluxThreat actors use this technique to hide their phishing and malware delivery sites behind a quickly-changing network of compromised DNS hosts. The DNS IP addresses are continuously changed within minutes. Botnets often employ Fast Flux techniques to effectively hide malicious servers from being detected.
Double IP FluxThreat actors use this technique to rapidly change the hostname to IP address mappings and to also change the authoritative name server. This increases the difficulty of identifying the source of the attack.
Domain Generation AlgorithmsThreat actors use this technique in malware to randomly generate domain names that can then be used as rendezvous points to their command and control (C&C) servers.

DNS Domain Shadowing Attacks

Domain shadowing involves the threat actor gathering domain account credentials in order to silently create multiple sub-domains to be used during the attacks. These subdomains typically point to malicious servers without alerting the actual owner of the parent domain.

1 Trackback / Pingback

  1. Virtual Private Networks - Cisco Education

Leave a Reply

Your email address will not be published.