Cousin Domain

What Is a Cousin Domain?

A cousin domain is a domain name that looks very similar to a legitimate brand’s domain but is slightly altered, often by adding, removing, or changing just one character.

Attackers use cousin domains to trick recipients into thinking a fraudulent message or website is from a trusted source. For example, if your legitimate domain is example.com, a cousin domain might be examp1e.com, example-support.com, or example.co.

This subtle resemblance makes cousin domains a popular tool for phishing, spoofing, and business email compromise (BEC) attacks.

How Cousin Domains Work

Cousin domains exploit human perception and visual similarity. When users glance at an email or URL, they may not notice small differences, such as:

• Letter substitutions (e.g., “m” replaced with “rn”)
• Extra or missing characters (e.g., “examplee.com”)
• Different top-level domains (e.g., “example.co” vs. “example.com”)
• Hyphenation or added words (e.g., “example-billing.com”)

Cybercriminals register these deceptive look-alike domains and use them to send fraudulent emails, host fake login pages, or intercept business communications. Because the cousin domain is technically different from the real one, traditional authentication measures like SPF and DKIM for the legitimate domain don’t apply.

Why You Should Monitor for Cousin Domains 

Cousin domains pose serious risks for both organizations and customers. They can damage brand reputation, lead to data theft, and cause significant financial losses through phishing or payment-redirect scams.

Monitoring and mitigating cousin domains is an essential part of domain protection. Proactive steps include:

• Regularly scanning for look-alike domains.
• Registering high-risk variations of your domain.
• Using authentication protocols like DMARC to prove which messages come from your legitimate domain.

While DMARC can’t block cousin domains directly, it helps mailbox providers identify and trust genuine emails, making impersonation attempts easier to spot.

Cousin Domains and DMARCeye

DMARCeye helps organizations detect the presence and activity of potential cousin domains by analyzing DMARC aggregate reports and sender patterns.

When DMARCeye sees email traffic claiming to be from your brand but originating from unfamiliar domains, it can highlight these anomalies and flag them for investigation.

Combined with your authentication data, this visibility enables you to spot impersonation campaigns early, strengthen your domain protection strategy, and safeguard your organization’s identity across the email ecosystem.

Sign up for a free trial of DMARCeye today and secure your email domain

To learn more about DMARC and DMARC-related terms, explore the DMARCeye Glossary.