Cybersecurity Q&A Series: How to Check if my Business Email Has Been Compromised?

Oct 29, 2025 | Information Security

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Throughout October, we shared insights around Copilot security, web form security, and AI phishing to answer common questions we get from clients and the wider business community. Now, as Cybersecurity Awareness Month comes to an end, we are wrapping up the series by answering a question that is very top of mind for many businesses: How can you tell if your business email has been exposed in a data breach?

With new data breaches making the headlines daily, many businesses are naturally concerned about the security of their emails and passwords. Even if you have not noticed suspicious activity, there is still a chance that your credentials have been leaked in a breach without your knowledge.

In this post, we will show you how to check whether your business email address has been compromised using trusted tools like Have I Been Pwned, and what steps to take next to protect your business.

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What can hackers do with your business email address?

Businesses naturally fixate on passwords because they are often described as the ‘keys to the kingdom.’ That can make a publicly known or leaked email address feel less urgent, but the risk is real.

Think about the number of accounts or platforms that your corporate email address might be linked to – internal cloud tools, financial systems, and vendor portals – making an email address a great starting point for ambitious attackers. Even without a password, hackers can use a valid business email for targeted social engineering attacks that can escalate into account takeover or data theft.

Below are some of the ways hackers can misuse an exposed business email.

Business Email Compromise (BEC):

In a BEC attack, hackers typically pose as C-level executives, HR or finance staff, or vendors to send emails that request fake payments, gift cards, or redirect legitimate invoices. These types of attacks leverage a sense of urgency and position of authority to pressure employees into taking damaging action.

Spread malware:

Once hackers have your corporate email address, they can send malicious or phishing emails to your employees to distribute ransomware or steal data.

Credential stuffing & unauthorized access:

Corporate email addresses are often linked to many business systems like cloud storage, intranet, SaaS platforms, remote collaboration platforms, and VPN portals. If your employees reuse passwords, attackers can try known password and email pairs from other breaches to break into these systems.

Hackers can also leverage the corporate email address to try and reset an employee’s password to gain access to their inbox or any connected accounts. If your business does not have strong password or multi-layer authentication policies, hackers can get the access they need for account takeover or fraud.

Dark web resale:

Exposed credentials are often sold or shared on dark web markets where other threat actors can repurpose them for further attacks.

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How to check if your business email has been compromised?

Now that you know not to underestimate the potential of a leaked business email address, let’s move on to the obvious question: How can you find out if your email address has been exposed?  One of the simplest first steps is to use Have I Been Pwned (HIBP), a trusted, free resource that is well respected in the cybersecurity community.

The site was founded in 2013 by Troy Hunt, a Microsoft Regional Director and Microsoft Most Valuable Professional, and international speaker on information security. HIBP aggregates data from breaches and allows users to easily assess where their data has been exposed.

By entering a business email address, domain, or user password, you can see whether it appears in any known data breaches. It’s important to note that even if your email address or domain is not found on the site, that is not a guarantee that your data was not exposed. For instance, if a breach goes undetected or breached data is never made public, it will not show up on HIBP. However, think of HIBP as an early warning signal that could alert you to a potentially harmful data leak.

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If your business email appears in a data breach, what should you do next?

If you find that your corporate email address or domain has been leaked, here are some immediate next steps you can take to minimize the risks to your business.

Identify which accounts are affected

Review the results from Have I Been Pwned to see where the email address appeared and whether the breach included passwords. Determine whether those credentials are used for any business-critical systems.

Change passwords immediately

Reset passwords for any affected employees accounts and any other systems where the same or similar credentials were used.

Enable multi-factor authentication (MFA)

MFA adds a strong second layer of security, even if passwords are compromised. Use authenticator apps or hardware keys instead of SMS where possible.

Audit for suspicious activity

Check for unusual login attempts, unauthorized forwarding rules, or unrecognized devices in your email and collaboration platforms (e.g., Microsoft 365).

Educate and alert your employees

Alert employees whose addresses appeared in breaches and ensure they are on the lookout for any targeted scams or phishing emails.

Run a dark web assessment

While HIBP indexes known breaches, a dark web assessment goes further. Security professionals can scan underground forums, marketplaces, and data dumps for credentials, internal files, or sensitive business data for more visibility.

Review your broader security posture

Assess password policies, account recovery settings, and access controls. Consider implementing domain protection protocols like DMARC to prevent email spoofing as well as a strong password manager to minimize password reuse or creation of weak passwords.
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Strengthen Your Security Posture

If your domain or corporate email addresses show up in a data breach, don’t panic. It doesn’t always mean someone’s inside your account, but it is a sign to tighten things up. Our Information Security team can help you run a dark web assessment, review your email security, and strengthen your business’ overall defenses. Contact us today to get started!

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