Subdomain Hijacking | CSC (2024)

FAQs

What is subdomain hijacking? ›

It's a cyber threat executed when an attacker gains control of a legitimate subdomain that's no longer in use, then cleverly exploits the forgotten or misconfigured dangling DNS to host their own content on the previously used zone.

Regularly Audit and Clean DNS Records

Regular DNS configuration reviews, especially CNAME and TXT records, are crucial. Removing or updating any outdated or irrelevant subdomain entries that point to third-party services that are no longer in use prevents vulnerable subdomains that attackers could take advantage of.

Subdomain takeover can have severe legal implications, as attackers may engage in illegal activities or host malicious content on compromised subdomains. It's crucial to report any such incidents to law enforcement authorities and take immediate steps to mitigate the risks to protect your reputation and users.

Subdomain takeover is essentially DNS spoofing for a specific domain across the internet, allowing attackers to set A records for a domain, leading browsers to display content from the attacker's server. This transparency in browsers makes domains prone to phishing.

Go to the DNS app. Locate the CNAME record for your subdomain, and click the 'Delete' button next to it. Confirm that you want to delete the record.

Let's say you are making a pitch to a client to create their new website. You can create a subdomain that is specifically intended for them to give an idea of what their new website might look like. This is hosted on your own main domain, while retaining ownership of the subdomain.

To identify DNS entries within your organization that might be dangling, use Microsoft's GitHub-hosted PowerShell tools "Get-DanglingDnsRecords". This tool helps Azure customers list all domains with a CNAME associated to an existing Azure resource that was created on their subscriptions or tenants.

Supply Chain Attacks: If the subdomain takeover affects a third-party service used by an organization, it can lead to supply chain attacks. Attackers can exploit vulnerabilities in the third-party service to compromise the organization's systems, data, or operations.

Subdominator is a dependable and fast open-source command-line interface tool to identify subdomain takeovers.

What is hostile subdomain takeover? ›

One of the subdomains of the scanned domain is pointing to an external service but the external service account was cancelled or has expired. Because the account is not in use anymore, an attacker can claim this account and takeover your subdomain. The attacker can use this subdomain for phishing or to spread malware.

A subdomain takeover occurs when you take over the service that some DNS records are pointing to. A DNS takeover occurs when you take over the DNS server that is assigned to that host. DNS takeovers are typically more severe because they give the attacker more control.

Subdomains are vulnerable to hijacking when a specific subdomain, such as “subdomain.example.com,” was initially configured to link to a specific online service like Amazon Web Services (AWS), GitHub, or similar platforms, but subsequently, this service is either intentionally removed or deleted by the user or owner.

Subdomains allow webmasters to organize their content, so they can maintain an ecommerce store on one domain, for example, and a blog on another. However, Google treats subdomains as separate sites.

Subdomain brute forcing involves using a list of common subdomain names and attempting to connect to them by appending them to a target domain. The success or failure of these connections is used to determine which subdomains are valid.

A subdomain takeover occurs when an attacker gains control over a subdomain of a target domain. Typically, this happens when the subdomain has a canonical name (CNAME) in the Domain Name System (DNS), but no host is providing content for it.

Subdomains are also commonly used to separate a section of a website from the main site. For example, blog.hubspot.com and shop.hubspot.com direct to our blog and online store respectively.

Example: "I responded to an urgent message about the expiration of our domain, but it wound up being a domain hijacking. Our website now shows really embarrassing content and I'm hearing of emails pretending to be me... saying inappropriate things."

Subdomain Spoofing: Attackers can create subdomains that appear to be legitimate but are actually fake. For example, an attacker could create a subdomain like “login.google.com.example.com” that appears to be a legitimate Google subdomain.