10 Ways to Detect a Business Email Hack – Before It’s Too Late

Imagine reconciling your bank statement to find $32K is missing from your bank account. No strange texts, no calls from your bank—just an empty balance and no explanation.

For many businesses, the attack started days, weeks, or months earlier, when a hacker got into their email. Once inside, the hacker can reset passwords, change banking details, and steal sensitive information without you realizing it.

If you suspect your email might have been compromised, don’t ignore that gut feeling. Here’s how to check for business email compromise (BEC) before the damage is done.

Who Sends and Receives Your Financial Emails?

Hackers don’t break into emails just for fun—they’re after valuable financial data and intellectual property.

Identify whose email account to investigate. Usually, the CFO’s email and the accounting department are good places to start. Search your Inbox and Sent Folder for signs of tampering.

What to Do:

Search for terms like: “bank,” “wire transfer,” “account login,” “password reset,” “invoice,” or “ACH.”
Look in your Sent folder. Are there messages you don’t remember sending?
Check for auto-forwarded messages. Were important emails forwarded to an address you don’t recognize?

If you find anything suspicious, act fast. The hacker may have already used your email to impersonate you.

Review Your Email Sign-In History

Email providers log every sign-in attempt, so you can see if someone accessed your account from an unfamiliar device or country.

Where to Check:

Gmail: Google Account Security → “Your Devices”
Outlook: Microsoft Account → “Sign-in activity”
Yahoo: Yahoo Account Info → “Recent activity”

Red Flags:

Logins from countries you’ve never been to
“Impossible travel” (e.g., logging in from New York and China an hour apart)
New devices you don’t recognize

If you spot anything suspicious, log out remotely and change your password immediately.

Look for Unauthorized Email Forwarding

Hackers sometimes set up email forwarding to secretly receive copies of your messages. This allows them to monitor your conversations, even after you change your password.

Where to Check:

Gmail: Settings → Forwarding & POP/IMAP
Outlook: Settings → Mail → Forwarding
Yahoo: Settings → More settings → Mailboxes

If forwarding is enabled to an unknown email, disable it immediately.

Scan for Hidden Filters or Auto-Deletion Rules

Hackers don’t want you to see bank alerts or security warnings, so they often create filters to delete them automatically.

Where to Check:

Gmail: Settings → Filters and Blocked Addresses
Outlook: Settings → Mail → Rules
Yahoo: Settings → More settings → Filters

Suspicious Rules to Look For:

Emails being moved to spam, trash, or archive automatically
Emails with words like “bank,” “wire transfer,” or “password” being deleted or forwarded

If you see anything like this, delete the filter immediately.

See If Your Email Was Leaked in a Data Breach

Your email might have been stolen in a breach long before any strange activity started. Hackers often buy and sell login credentials on the dark web.

How to Check:

Go to the Have I Been Pwned website and enter your email. If it appears in a breach, change your password immediately—and if you’ve used the same password elsewhere, change it there too.
Sign up for updates, so you know if your email is involved in future breaches.

Contact Banks and Vendors You’ve Shared Info With

If hackers got into your email, they may have stolen banking details from the emails you’ve sent. But here’s something most people don’t think about—what if the company you sent the info to was compromised?

What to Do:

Call your bank and payroll provider. Ask if they’ve seen any unauthorized activity on your account.
Reach out to vendors or clients you’ve sent financial details to. If their system was hacked, your info may have been exposed on their end.
Check if the wire instructions were changed. Hackers often replace your banking details with their own in invoices.

Check for Unusual Account Recovery Requests

Hackers often try to lock you out by changing your recovery settings.

Where to Check:

Gmail: Google Account Security → “Ways we can verify it’s you”
Outlook: Security settings → Advanced security options
Yahoo: Account Security → “Phone numbers and email addresses”

Signs of Tampering:

A new backup email or phone number you don’t recognize
Recent password reset attempts you didn’t request

If anything looks off, reset everything immediately.

Look for Strange Email Replies or Bounced Messages

If people are replying to emails you never sent, or if you’re seeing bounced-back messages for emails you didn’t write, your email is probably being used for spam or phishing. To confirm, check your Sent folder for messages you don’t remember sending.

Reset Your Passwords and Enable Multi-Factor Authentication

If there’s any sign of suspicious activity, change your password immediately. Turn on multi-factor authentication (MFA) to make it harder for hackers to get back in.

MFA requires a second step, like a text message code or an app notification, to verify your login. Even if hackers have your password, they won’t be able to access your account without this extra step.

Review Your Bank and Credit Card Statements for Suspicious Activity

Hackers often test the waters before making a big move. They might start with a small, unnoticed charge, sometimes as little as $1, to see if the card works before making a large withdrawal.

Go through your recent transactions and look for:

Small test charges
New subscriptions or auto-payments you don’t recognize
Transfers or withdrawals that seem unusual

Make this a daily practice. If you see anything strange, report it to your bank immediately.

Bonus: Call a Cybersecurity Expert

If your email has been compromised, you might need professional help to fully secure it. Hackers don’t always leave obvious signs, and sometimes they create backdoors that let them return later.

A cybersecurity forensics team can:

Trace how the hacker got in
Identify if other accounts were compromised
Help you lock everything down before more damage is done
Give you insights on how to keep your email and network safe

Protect Your Business Assets From Fraud

Cybercriminals aren’t just after passwords. They’re after money, data, and control. If you’ve had a security scare, you need a plan to protect yourself from future attacks.

Reach out today, and let’s make sure you’re protected.