Email is one of the most critical tools for businesses, but it’s also one of the most targeted by cybercriminals. A compromised email account can lead to lost data, financial fraud, or unauthorized access to sensitive company information. Knowing the warning signs and taking quick action can prevent major problems before they escalate.
In this guide, we’ll explain how to identify a compromised email account, what immediate steps to take, and how businesses can protect themselves in the future. We also provide links to trusted resources to help you understand and prevent email compromises.
1. What It Means When an Email Is Compromised
When someone gains unauthorized access to your email account, they can read messages, reset passwords for other accounts, or impersonate you to scam colleagues, clients, or vendors. Compromises usually occur through phishing attacks, weak or reused passwords, malware, or breaches of other services where your credentials were used.
For businesses, an email compromise can be especially damaging because attackers can often gain access to shared drives, internal systems, and financial accounts. Understanding how attackers operate can help you take proactive measures. For more detailed information, the Cybersecurity and Infrastructure Security Agency (CISA) offers a comprehensive guide to email security threats and best practices.
Additionally, Microsoft provides a thorough overview of account takeover risks and mitigation strategies that businesses can apply.
2. Signs Your Email May Have Been Compromised
Even non-technical users can spot many of the warning signs. Here’s what to look for:
Unfamiliar Login Notifications or Password Reset Emails
If you receive alerts about logins from devices or locations you don’t recognize, or password reset emails you didn’t request, treat it as a serious warning. These notifications often indicate someone is attempting to access your account. You can confirm unusual logins through your provider’s security activity pages:
- Microsoft 365: Account Activity
- Google Workspace: Security Activity
Reports From Contacts About Strange Emails
Clients or coworkers may tell you that you sent them suspicious emails, links, or attachments. Even if you don’t notice anything unusual in your sent folder, someone could be using your account to target others. Organizations like StaySafeOnline offer guidance on recognizing phishing and email scams.
Unexpected Forwarding Rules or Filters
Attackers often set up hidden forwarding addresses or rules to cover their tracks. These can automatically redirect emails or hide incoming messages so the compromise goes unnoticed. Checking and removing unfamiliar rules is critical.
Missing or Altered Messages
Emails that disappear from your inbox or sent folder, or drafts you didn’t create, can indicate unauthorized access. Maintaining regular backups, like those discussed in CISA’s Email Backup Guidelines, can help mitigate data loss.
Unexpected Multi-Factor Authentication (MFA) Prompts
If you use MFA and receive authentication requests that you didn’t initiate, it means someone has your password and is trying to log in. Declining the prompt and immediately updating your password is essential.
Unfamiliar Account Settings or Devices
New recovery email addresses, phone numbers, third-party apps, or connected devices you didn’t authorize are all signs your account may be compromised.
Presence in Data Breaches
Even if your email hasn’t been actively hacked, appearing in a leaked database means attackers could attempt to gain access. You can check using tools like Have I Been Pwned or Google’s Password Manager. Regularly monitoring these resources helps catch issues before they become critical.
3. What To Do If Your Email Is Compromised
If something feels off, handle the steps below in order. They are written specifically for people who don’t feel comfortable with technical instructions.
Change Your Password Immediately
Use a strong, unique password that isn’t used on any other site. Avoid simple phrases or patterns. The National Institute of Standards and Technology (NIST) offers guidance on creating secure passwords for business accounts.
Enable or Reset Multi-Factor Authentication
MFA dramatically increases security by requiring an additional verification step beyond your password. Microsoft reports that MFA prevents over 99% of account takeover attempts (Microsoft Security Blog).
Check and Remove Suspicious Rules or Forwarding
Even after a password change, mailbox rules or forwarding addresses created by attackers can continue sending your emails elsewhere. Open your settings, review the rules and forwarding sections carefully, and delete anything you didn’t create.
Review Login Activity and Remove Unknown Devices
Most email platforms allow you to see devices and sessions currently logged into your account. Remove anything unfamiliar to log out potential attackers. For businesses using Google Workspace, the Admin Console Security Reports can help track unusual activity.
Notify Contacts If Needed
If your account sent messages to others while compromised, inform them to prevent further phishing or scams. Resources like FTC Scam Alerts provide guidance on communicating about email fraud.
Scan Your Devices for Malware
Your email password might have been stolen by a keylogger or malicious program installed on your device. Running a full antivirus scan ensures your device isn’t still compromised.
Contact Your IT Team or Provider
If this is a work email, your IT department can investigate logs, audit connected systems, and secure additional resources that may be at risk. For small businesses without an internal IT department, consulting a managed IT provider can be a critical step in securing your operations.
4. How To Prevent Future Email Compromises
Prevention is much easier than recovery. Using a password manager eliminates the need to remember passwords and ensures every account has a strong, unique one. Enabling MFA everywhere stops the vast majority of unauthorized login attempts. Regular employee education on phishing and suspicious email recognition helps prevent human error, which is the most common cause of breaches (StaySafeOnline).
Quarterly account audits of login activity, connected apps, and mailbox rules help catch issues early. Limiting the use of public Wi-Fi without a VPN also reduces the risk of interception. Maintaining these practices as part of your company culture can significantly reduce the likelihood of future compromises.
5. Frequently Asked Questions
How can I quickly check if rules or filters were changed?
Go into your email settings and look for “Rules,” “Filters,” or “Forwarding.” Delete anything that automatically moves, deletes, or forwards messages that you didn’t set up yourself.
Does changing my password lock out hackers?
Usually yes, but attackers may still have access if forwarding rules or third-party connections exist. Always review these settings after a password reset.
Should I wipe my computer if my email is hacked?
Not always. Run a full malware scan first. Wiping the device is only necessary if malware is confirmed or the compromise was severe.
Can attackers read all my emails?
Yes, if they gained access. Acting quickly prevents further damage.
Does a compromised email put my other accounts at risk?
Possibly. Attackers often use email access to reset passwords on financial, business, or social accounts. Ensure MFA is enabled and review other accounts immediately.
Email security is one of the most important responsibilities for any business. By recognizing the signs of a compromise, acting quickly, and implementing preventative measures, you can protect your business, employees, and clients from unnecessary risk.
If you want to ensure your business is secure the experts at ITGuys are always happy to help!
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