The Modem Nobody Listed

OBSERVED

During an assessment at an energy campus, our team walked the site and found a 4G modem wired into a control screen. It gave that screen its own way to the outside world, one that never touched the site's network. A back door. On the same site, we also found remote-access tools open to the internet.²

We won't name the site, and we won't tell you more than we saw. The point is simple. The modem was there, and nothing on the network had flagged it.

How a modem ends up there

Modems like this usually show up for a good reason. A vendor wants to support equipment without sending a technician. A contractor needs remote access during commissioning. A remote site has no other way to report.

Then the project ends. The people move on. The modem stays. It keeps its connection, its default settings and its quiet path to the outside, long after anyone remembers why it's there.

One small modem. One unseen path.

It isn't only modems someone added

SOURCED

In 2025, Reuters reported that undocumented communication devices had been found in some solar power inverters, and cellular radios in some batteries.¹ Equipment can arrive with radios nobody wrote down.

Your inventory is built from what you bought and what you installed. A radio nobody listed isn't in it. You can't secure a connection you don't know exists.

A firewall can't control a connection that never passes through it.

Not every modem is a threat

Plenty of radio links are legitimate. Some are essential. The question isn't whether the modem should exist. It's whether it's known, approved, owned, and limited to the job it was put there to do.