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Sub-Domain Hijacking: What Is It and How to Prevent It

Updated: Jan 12, 2023

Sub-domain hijacking is a type of cyber attack in which an attacker takes over a sub-domain of a legitimate website to gain control of the resources associated with it. This type of attack is possible because of the way the Domain Name System (DNS) works. The DNS is the system that translates domain names into IP addresses, which are used to locate and access websites. In a sub-domain hijacking attack, the attacker is able to gain control of a sub-domain by changing the DNS records associated with it.


Sub-domain hijacking can be used to launch a variety of malicious activities, such as phishing attacks, malware distribution, and other malicious activities. It can also be used to redirect users to malicious websites or to steal confidential information.


In this article, we’ll discuss what sub-domain hijacking is, how it works, and how to prevent it.


What Is Sub-Domain Hijacking?


Sub-domain hijacking is a type of attack in which an attacker takes control of a sub-domain of a legitimate website. This type of attack is possible because of the way the Domain Name System (DNS) works. The DNS is the system that translates domain names into IP addresses, which are used to locate and access websites.


In a sub-domain hijacking attack, the attacker is able to gain control of a sub-domain by changing the DNS records associated with it. This allows the attacker to redirect users to malicious websites, phish for confidential information, or even distribute malware.


How Does Sub-Domain Hijacking Work?


Sub-domain hijacking works by exploiting weaknesses in the DNS system. The attacker first finds a vulnerable sub-domain of a legitimate website. The attacker then changes the DNS records associated with the sub-domain to point to a malicious server.


Once the DNS records have been changed, the attacker can then redirect users to a malicious website or use the sub-domain to launch phishing or malware attacks.


How to Prevent Sub-Domain Hijacking


There are several steps you can take to protect yourself from sub-domain hijacking.


1. Monitor your DNS records. Monitor your DNS records regularly to ensure that they are pointing to the correct IP addresses.


2. Use secure passwords. Make sure to use strong passwords for your DNS accounts to prevent attackers from gaining access.


3. Use multi-factor authentication. Multi-factor authentication adds an extra layer of security to your accounts and makes it more difficult for attackers to gain access.


4. Use a domain monitoring service. A domain monitoring service can help you detect any changes to your DNS records in real-time.


5. Use a web application firewall. A web application firewall can help protect your website from attacks by blocking malicious requests.


Example In Python Demonstrating Sub-Domain Hijacking


The following example demonstrates how an attacker can use Python to hijack a sub-domain.



# Import the necessary modules

import dns
from dns import resolver

# Define the domain name

domain = "example.com"

# Set the DNS server

dns_server = "8.8.8.8"

# Create a resolver object

res = resolver.Resolver()

# Set the DNS server

res.nameservers = [dns_server]

# Query the DNS server

answers = res.query(domain, "A")

# Check the answer

for rdata in answers:

# Check if the answer is an IP address

if rdata.rdtype == dns.rdatatype.A:

# If so, print the IP address

print(rdata.address)

# Set the new IP address

new_ip = "1.1.1.1"

# Change the DNS record

res.replace_rdata(domain, 0, dns.rdatatype.A, new_ip)

# Print a confirmation message

print("DNS record changed successfully!")


In this example, we use the Python dns module to query a DNS server and retrieve the IP address associated with a domain. We then use the replace_rdata() method to change the DNS record and point it to a new IP address. This allows the attacker to take control of the sub-domain and redirect users to a malicious website.


Conclusion


Sub-domain hijacking is a type of cyber attack in which an attacker takes over a sub-domain of a legitimate website to gain control of the resources associated with it. This type of attack is possible because of the way the Domain Name System (DNS) works. The attacker is able to gain control of a sub-domain by changing the DNS records associated with it.


To protect yourself from sub-domain hijacking, it’s important to monitor your DNS records regularly, use secure passwords, use multi-factor authentication, use a domain monitoring service, and use a web application firewall. The example in Python provided above demonstrates how an attacker can use Python to hijack a sub-domain.



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