The alarm didn’t go off. No flames. No broken machines.
Just silence.
One moment, the production line was moving smoothly. The next, everything froze. Screens flashed errors. Operators stood confused. Managers rushed to the control room. No one knew what was wrong.
At first, everyone thought it was a power issue. It wasn’t.
A technician finally said the words no one wanted to hear:
“Someone logged in remotely… and changed the system.”
No data stolen. No ransom demand. Just disruption. Yet the damage was real: missed deadlines, lost revenue, and shaken confidence.
The incident wasn’t dramatic enough for headlines, but it revealed something important. The machines weren’t just machines anymore. They were connected, automated and exposed in ways no one had noticed.
That day taught a simple truth
Modern OT systems are part of the network.
And if they’re connected, they can be attacked.
So the real question became.
How do you stop this from happening again?
Below are practical steps drawn from real-world failures like this one. They aren’t theory. They’re lessons paid for through downtime.
1. Separate Your IT and OT Networks
If everything sits on one flat network, an attacker only needs one weak point.
Separate them. Control the connection points. Treat OT like a locked room, not a hallway.
2. Know Every Device Connected to OT
Most factories run systems older than their staff. Some devices have never been documented.
Create an inventory. Track versions, firmware and connections. You can’t secure what you don’t know exists.
3. Limit Access - Especially Remote Access
No shared passwords. No “default admin” settings.
Give access only when necessary, not permanently. Use multi-factor authentication for remote vendors.
4. Harden Devices
Turn off services no one uses. Remove default accounts.
A simple configuration change can stop an attacker before they start.
5. Patch Carefully - But Don’t Ignore It
Updates can cause downtime, so patching needs planning.
Test first. Prioritise high-risk systems. Balance safety with security.
6. Monitor for Strange Behaviour
Most OT attacks start quietly. Small changes. Odd timing. Unusual connections.
Monitoring makes these changes visible before they grow into failures.
7. Secure Remote Access Properly
Avoid open VPN access.
Use jump hosts, session recording and temporary access windows. When remote access isn’t needed, it should be off.
8. Lock Down Engineering Workstations
These systems can control everything. Treat them like critical assets.
No USBs. No games. No browsing. Only what is needed to run operations.
9. Plan for the Worst Before It Happens
When something breaks, panic isn’t a plan.
Create an incident response workflow. Assign roles. Practice it. Fix the gaps.
10. Train People - Then Train Them Again
Technology won’t save you if people hold the door open.
Educate engineers, operators and contractors. Awareness reduces mistakes.
OT security isn’t about fear. It’s about preparation.
The factory that shut down wasn’t attacked because someone wanted the data. It happened because the system was exposed, and no one realised it.
As OT and IT merge, the old assumption that “machines are safe because they’re isolated” no longer holds.
Security is now part of reliability.
And reliability is what keeps operations running.
If the silence ever comes to your factory, make sure it isn’t because someone found a switch you never secured.
