HN.zip

Show HN: Coldframe, a honeypot that poses as a supermarket fridge controller

I built Coldframe, a honeypot that pretends to be a supermarket refrigeration controller. Inspired by the events on industrial fridge installations in the past weeks, I wanted to see what people would try against a convincing fake.To learn more about this I built a honeypot that resembled perfectly the Danfoss AK-SM 800A and Dixell XWEB interfaces. Both of them are recognized on Shodan as real ones (an not as honeypots). It’s one Python file using only the standard library, and it builds on eppser/danfoss-ak-sm-decoy and public research by Synacktiv, Claroty and Ironhackers.Things that were fun to get right:- Matching real units. I used Shodan records of real devices to match header order, page titles, certificate fields and TLS versions. The Danfoss persona sends nginx headers in the same order as a real AK-SM 800A. The Dixell persona sends no Server header and pads its page to exactly 8,202 bytes.- Recognising exploit attempts. It recognises CVE-2025-41450, the Danfoss “code of the day” login bypass, and records whether the submitted code is correct for today. It also tags attempts targeting three other Danfoss CVEs and the XWEB vulnerabilities.- Letting them in. Default logins open a fake store dashboard with defrost buttons, so you see the second move, not just the first. Nothing behind it is real.Two instances have been live for a day. So far they’ve only seen generic scanners and Shodan’s crawler, which is called refrigerator.census.shodan.io.Feedback welcome, especially from anyone who has seen these devices in the field!

261 points by - 63 comments

63 Comments

[3 hidden]5 mins ago
I would be very skeptical of anyone relying on Shodan data. At one point I was trying to write honeypots myself by replicating wifi cameras, but almost all the ones on the internet I found were honeypots of some sort, and the ones that weren't were already hacked and had their web pages replaced. In retrospect it would have probably been better to get a vulnerable device myself and probe it.

If I were you, I would probably ensure that the fridges you used have residential or commercial (aka non-DC) IP addresses. Maybe Shodan uses this data for their "honeypot" label, my experience was some time ago so no idea though.

[3 hidden]5 mins ago
At this point the honeypot I'm running is not marked as honeypot. Guess that it's a good sign?
[3 hidden]5 mins ago
What I meant is that I'd find some way of ensuring that I'd want to ensure that the responses you're serving up are real. If you are happy with what you have, we're good.
[3 hidden]5 mins ago
Fair point and I agree, Shodan isn't the only source. For the reason, for Danfoos the login page comes straight from the firmware package that Danfoss publishes. It's byte for byte identical, so it hashes the same as thousands of real units. Dixell was matched against Shodan records, so that one is weaker, you’re right.

The datacenter IP is the bigger tell. Real controllers sit on shop or ISP connections. Moving one decoy onto a residential line is on my list.

Along the way I did some hunting for vulnerabilities on the Danfass units, quite interesting stuff actually.

[3 hidden]5 mins ago
Did AI write this comment?
[3 hidden]5 mins ago
The tell is the biggest tell. xD
[3 hidden]5 mins ago
Danfoss was misspelled, so probably not.
[3 hidden]5 mins ago
An extra insight, there was some news of 'blood banks' also being targetted. This is possibly a stronger (painful) target. It would demorelize people that are donors. https://www.independent.co.uk/tech/security/blood-hack-fridg...
[3 hidden]5 mins ago
Why would it, scarcity generally motivates
[3 hidden]5 mins ago
[flagged]
[3 hidden]5 mins ago
> fluid market

Heh.

[3 hidden]5 mins ago
Plot twist: the hackers are members of the Van Helsing Society and the supermarkets were just a trial run in their war against the International Vampire Cabal.
[3 hidden]5 mins ago
One thing keeps coming back, (and it's the story of industries where security and patching is an afterthought).

a supermarket has no security team. If a fridge controller needs patching, a VPN and a strong password to be safe, that work has to come from the vendor or installer by default. One would hope that all these come by default or as a feature on these devices. It could even be a selling feature and not part of an expensive maintenance contract. A supermarket manager cannot be expected to do this work.

[3 hidden]5 mins ago
This is how it should work: supermarket wants to use high tech stuff such as connected fridges, they get a cyber insurance policy as part of all the other insurances they have. The insurer then has domain experts to figure out what the insured needs to do to meet a risk threshold (or they adjust fees accordingly).

This model has worked fine for many other types of risks.

[3 hidden]5 mins ago
In practice this insurance (which already exists!) just creates another compliance checklist and not a meaningful focus on actual security.
[3 hidden]5 mins ago
Many of these supermarkets are part of big brands but operate independently. I doubt cyber insurance is top of mind for those small owners
[3 hidden]5 mins ago
It will be soon. How many refrigerated cases of product can they afford to lose?
[3 hidden]5 mins ago
Not to mention other ways cyberattacks can paralyze their business, eg. their POS system
[3 hidden]5 mins ago
That seems pretty location dependant. In Australia at least the two major supermarket chains are not insignificant (e.g. EBITDA ~$5 billion and ~$2.6 billion) and have large internal tech and cyber teams.

I think this is more indicative of the plethora of technical debt and straight up technical negligence that's accompanied the past 10-15 years of internet connected everything. What's happening today is the predictable result of project based works funded by capex deploying assets (of all types) with no consideration of opex funding for the technology components.

Just because a webserver is running in some physical device (fridge, camera, vacuum, washing machine, pump controller, lighting system, audiovisual equipment, access control system etc) does not magically exempt it from the same sort of ongoing sysadmin and maintenance you'd expect as a baseline for something running on standard compute. That applies equally to manufacturers publishing firmware, and the asset owners/service companies that have the responsibility to apply.

[3 hidden]5 mins ago
Agree with all of what you're saying, wholeheartedly.

But I keep coming back to: why do supermarkets need networked freezers anyway? Most supermarkets are open most days, with long hours. Can't any adjustments just be done manually by staff on the rare occasions when that is needed? I've seen some people argue that the major usecase is defrosting. But when you're defrosting, you certainly have lots of people on site engaged in emptying the fridge in question. Surely flipping the thermostat is a rounding error as far as costs go?

[3 hidden]5 mins ago
Networking freezers is good for:

* continuous monitoring and logging of the freezer's temperature (supermarkets are obliged to do so)

* sending alerts when something's off

Regarding the defrosting: Commercial freezers can defrost while the groceries stay in, just like the "No-Frost" freezer at home.

[3 hidden]5 mins ago
I work at a company that sells security software, and one of our customers is a major grocery chain. They definitely have a security team, I’ve talked to them.
[3 hidden]5 mins ago
Can't open the link, GitHub is down:

    503 Service Unavailable
    No server is available to handle this request.
[3 hidden]5 mins ago
Why?
[3 hidden]5 mins ago
i think it would be pretty trivial to determine the box is a pot from whois etc.

people who target these supermarket chains etc. are doing just that. not scanning the entire internet and popping all the fridges, but doing targeted attacks.

mostly your pot will just be a +1 on benign peoples scanners.

you want honeypots for things that are mass exploited, not for things used in targeted attacks.

just my 2 cents. respect the project can be fun to do ofc but i wouldnt expect much interesting results.

that being said maybe you can find parties who secure these chains, or themselves, and offer it as a TI sort of service. Seeing as they knew about these vulns for many months before they got hit, its unlikely they will pay for it or be interested.

[3 hidden]5 mins ago
Great input, thanks! My next step is to deploy on a normal ISP and not on a cloud provider. Just let it sit there. I think we should give back to those companies as much as possible. OT is not where the big money is and all security experts are flocking to. I've already started some actions in this direction btw.
[3 hidden]5 mins ago
Not a headline I ever expected to read. 2026 has been a wild year.
[3 hidden]5 mins ago
It's been a wild year from a suburbanite perspective. There's still a long way to go before real wilderness is witnessed.
[3 hidden]5 mins ago
The interesting aspect of these attacks was that they seemed to have been done per country.
[3 hidden]5 mins ago
Super cool, especially showing your work as FOSS, but: why announce your honeypot before it’s fulfilled its intended purpose once?
[3 hidden]5 mins ago
The more people that can deploy it, the higher the chance of discovering something about the attacks. Also this gave me an incentive to look deeper into the real software.
[3 hidden]5 mins ago
You'd probably have more luck posing as other industrial hardware like HVAC, lighting, controllers for the kinds of pumps or valves you'd find in chemical plants. That kind of stuff.
[3 hidden]5 mins ago
New ideas are popping up. I started with fridges because of the recent attacks, but the code makes it easy to add personas. Electric car charing stations and coffee machines were my initial idea, but HVAC and building controllers are probably better ideas. Thanks!
[3 hidden]5 mins ago
Did you write this post with AI?

- Letting them in. Default logins open a fake store dashboard with defrost buttons, so you see the second move, not just the first. Nothing behind it is real.

Given the context, this reads like vomit.

[3 hidden]5 mins ago
Both the post and the comments. It's cringe. Just write what you have to write, author.
[3 hidden]5 mins ago
Of course they did. That text is Claude.
[3 hidden]5 mins ago
Did anyone else notice the badge at the top of the GitHub README.md?

    > HackerNews: #1 Repo of the Day - 214 points
Here is the link from the README.md:

    <img src="https://hackergit.org/badge/hedgerow-dev/coldframe.svg?style=rank&rank=day" alt="Hacker News" width="250" height="55">
Something about it is cringe to me. It is giving LinkedIn self-promotion vibes.
[3 hidden]5 mins ago
Very cool. Seems like this is the modern hacker version of "is your refrigerator running?"
[3 hidden]5 mins ago
The hilarious thing about this is that there was an initial hack, and then like a month later another one that was equally successful. Who could have possibly seen that coming lol.

> Default logins open a fake store dashboard with defrost buttons, so you see the second move, not just the first.

I think we're past the point where it's reasonable to expect people to not use AI for code, but their prose still sucks balls. You should at least write your submission here yourself, come on.

[3 hidden]5 mins ago
I agree, I rushed this one a bit. Glad to share with the industry at least.
[3 hidden]5 mins ago
TBH, I think at this point it is the "holier than thou" people pointing out every instance of slightly AI sounding text that are getting annoying.

I was happy reading you post and I imagine there are many many more people like me than the grinch.

[3 hidden]5 mins ago
Thanks! To be honest, using AI helps 'gettings things out' instead of shelving it because it's never perfect.
[3 hidden]5 mins ago
I have met super intelligent people who speak multiple languages but need a bit of help writing stuff in English.

I have no idea who you are, but I would rather give you the benefit of the doubt then try to get a dopamine hit by attacking you.

[3 hidden]5 mins ago
While it might help you get things out faster, it's still counter to this one fundamental rule:

If you couldn't be bothered to write it, I can't be bothered to read it.

[3 hidden]5 mins ago
> I think at this point it is the "holier than thou" people pointing out every instance of slightly AI sounding text that are getting annoying.

I don't think it's unreasonable to spend literally 3 minutes writing your own submission. I'm not asking to rewrite every code comment.

And it wasn't "slightly" AI sounding text. It's very obviously AI.

[3 hidden]5 mins ago
Crazy thing is, when the fridges in all those military bases were hacked people were initially in denial and the people noticing that it was just a little too coincidental to be happing simultaneously were called paranoid. Well who's paranoid now?
[3 hidden]5 mins ago
Me reading it be like:

MFs be doing everything but pulling those fridges off the Internet. Given the amount of TOR nodes, IP addresses today, Honeypots mean nothing ....

Of course, it's my unpopular opinion. :)

[3 hidden]5 mins ago
Agreed, that's the real fix. The honeypot is just to see who's looking while they're still out there.
[3 hidden]5 mins ago
Honeypots are not there to prevent or disrupt attacks. You use them to collect interesting interaction samples. The author is not running any real fridges or making any choices about protecting them.
[3 hidden]5 mins ago
Wait, I recall reading the threads about someone speculating there was a hack. Some people suggested it could just be that a large percentage of refrigeration units received a software update at the same time which resembled a hack.

Is there a definitive story that someone actually did hack these units on a grand scale?

[3 hidden]5 mins ago
There have been (at least) two separate waves to this now, which makes the "innocent broken update" speculation much less likely?
[3 hidden]5 mins ago
Unless they push updates in waves, which is what most big rollouts do.
[3 hidden]5 mins ago
That's a known playbook. Stir up shit, then create an uplausible denial which will take experts some time to debunk. Once it's figured out the story was bs, put out another three. By the week end there is 10 narratives and nobody except the field experts is sure that it's the usual suspects doing the usual things, but nobody listens to those
[3 hidden]5 mins ago
Examples of this happening in the past?
[3 hidden]5 mins ago
I believe the most documented example is mh17
[3 hidden]5 mins ago
This type of attack lasted few days in different countries, quite hard to believe the fridge manufacturer could keep pushing these updates after all the news around.
[3 hidden]5 mins ago
Fwiw, the first thread I recall was a speculative blog post about commissary freezers for the US military: https://news.ycombinator.com/item?id=49508506
[3 hidden]5 mins ago
That's the first of four incidents I've seen in the news recently. As far as I know it's the one that could have been some other kind of correlated failure (bad update, calendar bug, whatever). We don't know much about it.

After that were two separate supermarket events, which I think were both linked to the known Danfoss vulnerability (CVE-2025-41450); and most recently a blood bank event.

[3 hidden]5 mins ago
Now, as of November 2026, it is confirmed as a hack.

Confirmed exploits, many manufacturers, experts, …

[3 hidden]5 mins ago
My view is that some companies installing this have not implemented any defense in depth and cut corners all around. Installing a firewall with a simple vpn service would probably have prevented lots of pain (unfrosting). In general we also see almost every security expert working at banks or other high paying companies and not for supermarkets. My feeling is that this 'niche' is probably interesting to spend some 'tokens' and time on.
[3 hidden]5 mins ago
> Is there a definitive story that someone actually did hack these units on a grand scale?

Given the scope here (see map at https://en.wikipedia.org/wiki/2026_French_supermarket_refrig...), it'd either be individual hackers getting inspired from their neighbor hackers, or one actor targeting European countries.

Although seemingly the hack wasn't so sophisticated, maybe it's truly just some kids fucking around with what they see being open, and maybe just want to target European countries for the "lulz" or whatever, who knows.

[3 hidden]5 mins ago
It's most certainly a form or hybrid warfare. While being very easy to perform, it's still quite effective. Empty supermarkets and supply chains being disturbed. Hopefully this is a wakeup call for the industry.
[3 hidden]5 mins ago
> Hopefully this is a wakeup call for the industry.

Would be nice but none of the other <waves at cybersecurity for the last decade> events has been.

It seems like something horrific is going to have to happen before this is taken as seriously by government and private orgs as it should have been, that seems to be how it works with other stuff historically.