Sierra Wireless AirLink LX40: Ransomware Risk, Voltage Testing, and IoT Device Questions

What this guide covers

If you're deploying a Sierra Wireless AirLink LX40, or you're responsible for any connected device that sits on a network, these are the questions I get asked most. I've been in the field for about nine years, coordinating emergency deployments for public-safety and industrial clients. I've handled 200+ rush orders, and I learned the hard way that “it worked in the lab” is not the same as “it works at 2 a.m. in a substation.”

Here's the thing: this isn't a sales brochure. It's the checklist I wish someone gave me before my first AirLink deployment. Skip the part you don't need. Keep the part that keeps you from getting a 4 a.m. call.

The questions I actually get

• Does “Sierra Wireless ransomware” mean my AirLink LX40 is at risk?
• How to use a multimeter to test voltage on a Sierra Wireless AirLink LX40
• Can a blood pressure monitor device connect through the AirLink LX40?
• Power LED is on, but the gateway keeps rebooting. What now?
• What should I check before deploying any connected device?

1. Does “Sierra Wireless ransomware” mean my AirLink LX40 is at risk?

“Sierra Wireless ransomware” is a search phrase that usually points to one event. In 2020, Sierra Wireless reportedly had to pause operations and take systems offline after a ransomware attack. That event was about corporate IT, not an inherent flaw in every AirLink router. But it should still be a wake-up call: a security incident at a vendor can ripple through your supply chain, and no brand is untouchable.

Here's what I actually do before a deployment. First, inventory every device and record current firmware. Second, change default credentials and disable any management interface that can be reached from the public internet. Third, make sure the device is configured to check for signed firmware updates. “Enterprise-grade” means you have tools to secure it. It does not mean “you can ignore it.”

I have mixed feelings about remote management. On one hand, being able to reboot a gateway from my truck is a lifesaver when a site is two hours away. On the other hand, that same remote access is an attack surface. After too many years of seeing port forwards used instead of VPNs, I now require a VPN or private APN for any management access.

Per FTC guidelines (ftc.gov), a security claim has to be truthful and substantiated. So when a vendor says “secure,” ask what exactly that means and which threats it covers. In my experience, ransomware success in IoT deployments comes down to one of three failures: default passwords, exposed management ports, or delayed patching. Fix those three and you have reduced most of the risk. Not all of it, but most of it. That's the game.

Short version: don't panic about the phrase “Sierra Wireless ransomware.” Use it as a reminder that security is a process, not a sticker on the box.

2. How to use a multimeter to test voltage on a Sierra Wireless AirLink LX40

When I first started doing installs, I assumed a glowing power LED meant the gateway was getting clean power. I was wrong. Two “mystery reboot” calls later, I learned to check voltage before swapping a router.

Here's how to use a multimeter to test voltage on an AirLink LX40 power feed, step by step:

1. Turn off power to the gateway. If you're testing the power supply separately, disconnect it from the gateway before you put probes anywhere.
2. Set your multimeter to DC voltage. On most meters, that is a V with a straight line above it. If you only have a manual range dial, choose a range above the expected voltage. For a nominal 12V supply, the 20V DC range is a good choice.
3. Plug the black lead into the COM jack and the red lead into the VΩmA jack. This is the same setup for almost every voltage measurement you'll do on a router or modem.
4. Place the black probe on negative or ground, and the red probe on positive. On a barrel connector, the center pin is usually positive and the outer sleeve is negative, but verify the label on the power supply. Do not assume.
5. Read the display while the probe tips have solid contact. A 12V supply should read around 12V DC. It should not read 0V, and it should not be way below nominal under load.

If you see 0V, check the fuse, wiring, and power supply before blaming the Sierra Wireless device. If you see voltage that's off—say, 9V on a 12V rail—fix the power source first. A modem can boot on low voltage, then reboot when it tries to transmit because the supply collapses.

For AC outlets, switch to AC voltage, but the LX40 itself is a DC-powered device. You are usually in DC land. And be honest about your comfort level: if you don't know which lead goes where, stop and have someone show you. It takes five minutes to learn and the payoff is huge.

5 minutes of verification beats 5 days of correction.

3. Can a blood pressure monitor device connect through the AirLink LX40?

This one surprises people. A typical blood pressure monitor device is not a network device. It is a Bluetooth or USB peripheral. The AirLink LX40 is a router, not a Bluetooth hub or a health-app server. So the answer is: maybe, but not directly.

If your blood pressure monitor device has its own cellular module, like many LTE-M health monitors do, it does not need the LX40 to connect. It needs its own SIM and coverage. The LX40 can stay in the same cabinet, or not, and it won't matter much. The device talks to the cell network on its own.

If the blood pressure monitor is Wi-Fi or Ethernet enabled, you can put it on the LX40's LAN segment just like any other device. Give it a reserved address, make sure the Wi-Fi encryption is on, and test the connection before you mount the router on a wall.

If the device only speaks Bluetooth, you need a bridge—a phone app, a Bluetooth-enabled gateway, or a USB dongle on a computer. The LX40 cannot pair with it. I made this mistake on a pilot project years ago. We had a stack of connected health devices and a shelf full of expensive routers, and assumed they were one happy family. They weren't.

So read the datasheet first. That is the whole answer.

4. Power LED is on, but the Sierra Wireless AirLink LX40 keeps rebooting

When I'm triaging a rush deployment, this is the call I get at 11 p.m. The router has power. The LED is on. But it reboots itself like it's got a bad power supply or a loose connection.

First thing I check is voltage under load. A bench power supply can read 12V when nothing is connected, then drop to 8V when the modem starts transmitting. You need to see what the voltage does during boot, not just at idle. If it dips hard, replace the supply or the wiring.

Other causes I've found in the field:

• Loose terminal block connections (more common in vehicles than you'd think)
• A power adapter with the right plug but the wrong voltage
• A short on the ignition sense line, if the gateway is wired to a vehicle's ignition
• Corrupted configuration after an interrupted reboot
• A damaged SIM slot or SIM card that makes the modem re-register repeatedly

Notice what's not at the top of the list: “the router is bad.” It can be, but I've seen far more bad power issues than bad modems. The fix is simple: verify power first. Replacing a Sierra Wireless gateway is expensive. Testing voltage is free. And if you skipped the multimeter step, now is the time to go back to it.

5. What should I check before deploying any connected device?

Look, I used to think rushed deployments meant skipping the boring checks. Then in March 2024, 36 hours before a public-safety demo, I found a gateway that had been sitting in a warehouse for a year. The firmware was ancient. The certificate was expired. The whole project almost went down because nobody checked. We fixed it in time, but it was not fun.

My current pre-deployment checklist is simple:

• Update firmware while the device is still on the bench.
• Change default passwords and store them in a real password manager, not a sticky note.
• Disable WAN-side web access. Always.
• Test voltage with a multimeter before you mount the device.
• Label SIMs and write the APN on the deployment sheet.
• Do one full reboot test after configuration.

That last one catches the “it works until it restarts” problem. I don't have hard data on how many deployments skip these steps, but based on the 200+ sites I've visited, my sense is at least a third are missing one of these. That's not meant to shame anyone. It's just reality. A checklist is the cheapest insurance you'll ever buy.

And that's the prevention-over-cure point: check before you ship, not after the client calls you at 2 a.m.