Email Thread Hijacking: How Systems Are Being Hacked and How to Prevent It
One of the most prevalent (and growing) forms of email fraud that targets businesses today is Email Thread Hijacking. It’s sneaky, difficult to see and dangerous. Cybercriminals are getting cleverer; they’re not sending random spoof emails any more. They’re diving right into your actual conversations.
Here’s the full breakdown, so you know what’s happening — and how to put a stop to it.
1. Why Email Thread Hijacking?
Thread Hijacking (also sometimes called Email Thread Hijacking) occurs when a hacker hijacks a conversation you were having with a coworker, a client, or a vendor by spoofing their email address. Rather than starting a new email from the ground up, they reply into a thread that is already in motion.
Why is that dangerous?
Because you’re more apt to trust an email that’s a part of a familiar thread — especially when the message is sent by a legitimate contact in your address book.
Here’s how it generally works:
- You’ve been ping-ponging by email with a vendor about an invoice.
- A hacker compromises one of your mailboxes ( you or the vendor).
- They insert themselves right into the middle of that conversation and send what seems like a genuine follow-up.
- That follow-up is an attached malware, a phony payment link or fake payment information.
And just like that—your network is compromised or your cash is pilfered.
2. How Hackers Exploit Emails That Are Ongoing
So how do hackers manage to do this? Let’s go step-by-step.
1. Initial Compromise
To start, the attacker gains access to someone’s email account. This usually happens through:
- Phishing emails
- Weak passwords
- Compromised credentials purchased on the dark web
- Password theft malware
Once in, the hacker keeps his mouth shut and watches. They scour inboxes, study how people talk and choose when to hit.
2. Email Thread Infiltration
Once they’re inside, they come across an existing email conversation — usually one with financial or confidential material.
They respond to the thread with carefully worded messages. It appears to be from you or your trusted contact. The message might say:
- “Hello, please find the updated invoice attached.”
- “Please send payment to our NEW bank account below.”
- “Tell me when the wire transfer is complete.”
And the message wont rouse red flags, because:
- It’s in the correct thread
- The tone sounds normal
- The email address may even be correct (if they had full access to the account)
3. Delivery of Malware or Scams
This is when the fraud occurs. They either:
- Email malware [malware in an attachment (Word doc, PDF, Excel)]
- Make a person click on a fake link
- Harvest account credentials using a phishing login form
- Divert payment to a fraudulent account
And since its in a trusted email thread—you or your employees may never question it.
3. How to Detect & Prevent It
None of it is foolproof, but we can certainly make it more difficult for them.
👁 How You Can Recognize Email Thread Hijacking
Watch out for these red flags:
- Unexpected attachments in a thread that did not previously include files
- Requests that appear urgent, such as “make payment now” or “change bank account immediately”
- Typos or minor language shifts in a formerly formal-sounding thread
- Links that appear to be normal yet redirect elsewhere when hovered
- A change in the tone or style of email (doesn’t fit previous conversation)
🛡 How to Prevent It
These are simple steps you can take to improve your cybersecurity protection:
1. MFA Everywhere
- Use Multi Factor Authentication on every email account
- It prevents hackers from getting in, even with your password
2. Train Your Team
- Train staff to spot phishing and suspicious activity
- Alert them on changes in payment instructions
3. Email Filtering
Use a good email security solution that can identify thread hijacking, malware, and spoofing
4. Secure Your Devices
- Update antivirus and firewalls
- Regularly patch software to mitigate known vulnerabilities
5. Limit Access
- Provide email access only to those who truly require it
- Use role-based permissions
6. Audit Frequently
- Inspect who is accessing your systems regularly
- Create alerts regarding unauthorized activity or log in from unusual locations
4. Email Security Solutions from PJ Networks
At PJ Networks we see the harm caused by email fraud day in and day out. That’s why we developed our very own strong line of defense to prevent threats from reaching your inbox.
Here’s how we can help:
- ✅ Real-Time Threat Scanning
Our tools do not wait, they scan email threads in real time for malicious attachments, links and headers. - ✅ Behavioral Analysis
We analyze threads to observe communication patterns that can predict unexpected responses, such as a hacker entering a thread. - ✅ Spoofing and Impersonation Prevention
Block emails that appear to be from your CEO or vendors but are not - ✅ Data Loss Prevention (DLP)
Identify attempts to send sensitive client data, financials or passwords - ✅ Easy Admin Dashboard
An intuitive control panel to review threats, manage settings, and protect your whole team
Email security is one of your most crucial defenses, whether you’re a small business or a large enterprise.
We don’t just block threats. Our monitoring and reporting—and then adaptation—keep you ahead of the curve.
5. Conclusion
And Email Thread Hijacking is one of the most dangerous—and convincing—forms of email fraud that businesses are facing today. It is an exercise in social engineering and technical ability, and its incredibly difficult to detect if you dont know what you are looking for.
The good news? Now you do.
If you want to keep your business away from data loss, financial fraud as well as massive disruptions, the things you can do are securing your email systems, training your team as well as working with someone like PJ Networks.
Go ahead and make cybersecurity protection your number one priority.
In addition — Email Thread Hijacking is real and it’s here. Do not allow it to take your data or your money.
