Also referred to as DNS cache poisoning, Domain Name Server (DNS) spoofing is a form of computer security hacking in which false information is placed in a DNS resolver cache. Altered DNS records are used to redirect online traffic to a fraudulent website that resembles its intended destination.
With DNS spoofing, unsuspecting victims end up on malicious websites. Once there, victims are prompted to login into their account (or a false version of it), giving the attacker the ability to steal their credentials and other types of sensitive information. The malicious website is also used to install worms or viruses on a victim’s computer, giving the attacker long-term access to both the computer and the data it stores.
How DNS spoofing works
A DNS server translates human-readable domain names into numerical IP addresses so that computers can process them. This is used to route communications between nodes. If the server does not know a requested translation it will ask another server, with the process continuing in a circular pattern. To increase performance, a server will cache these translations for a certain amount of time.
When a DNS server has received a false translation and caches it for performance, the false translation is considered to be poisoned and it supplies false information to clients. If a DNS server is poisoned, it will return an incorrect IP address, diverting traffic to another computer, often an attacker’s.
Methods for DNS spoofing
- Man-in-the-middle attack: An attacker steps between the web browser and DNS server to infect both simultaneously. The result is a redirect to a malicious site hosted on the attacker’s own local server.
- DNS server hijack: An attacker directly reconfigured the server to direct all requesting users to the malicious site. Once a fraudulent DNS entry is injected onto the DNS server, any IP request for the spoofed domain will result in the fake site.
- DNS cache poisoning via spam: The code for cache poisoning is typically found in URLs sent via spam emails. These emails attempt to frighten users intp clicking on the URL, infecting their computer. Banner ads and images can also send users to this code. Once poisoned, the computer will take users to the fake website spoofed to appear like the real site.
Preventing DNS spoofing
Website owners and service providers can prevent DNS spoofing by:
- Investing in DNS spoofing protection tools
- Using domain name system security extensions
- Using end-to-end encryption
Endpoint users can prevent DNS spoofing by:
- Avoiding clicking on an unrecognized link
- Regularly scanning a computer for malware
- Flushing the DNS cache to solve poisoning
- Using a Virtual Private Network (VPN)