SIMmetry

When I learned that the Secret Service had taken down a giant “SIM farm” in the NYC area, I immediately had two thoughts: One, “Wow, that sounds like the reason we all get so many scam calls.” And two, “Holy crap, what is that weird-ass piece of hardware?!?!??!?!??!?!??!?!?”

You must understand, dear reader, the bizarre gear they were using. I’ve never seen anything like it before.

Much will be written about the threat to the telecom system, which is the angle the Secret Service is taking, as it was uncovered right around the time of a United Nations General Assembly meeting. I want to know the deal with the hardware itself.

You know the old board game Guess Who? You know, with the cards that stick up, and the other player has to guess what faces you have? Imagine that times 100, but with the cards a 20th of the size of the Guess Who cards, and add a whole freaking ton of antennas into the mix, and you have this crazy-ass device, the niche-iest of niche electronic devices. Each device holds numerous SIM cards, which means that someone had to pop out thousands of SIMs to put in these boxes, presumably one at a time.

Fortunately for us, the U.S. Secret Service gave us a picture of that insanity, too:

So basically, we have a device that is intended to hold literal hundreds of SIM cards, and apparently the people who ran this network had literal racks of these machines. They have this almost magical sense of symmetry to them, which makes them highly attractive to nerds like me. It reminds me of Aereo, the noble (but failed) attempt to use thousands of tiny antennas to capture broadcast television signals to resell online.

So, what the heck is this thing, why did they have so many of them, and how come you’ve never seen them before?

The short answer: It’s a device called a “SIMbank” or “SIM gateway,” often attached to a “SIM pool,” which gives all those SIM cards access to a cellular network.

The longer answer: The devices in the Secret Service photo, apparently made by a Chinese company called Ejoin Technology, are used in VoIP settings to handle lots of SIM cards. Ejoin says they produce the devices for what it calls “SMS and voice gateway solutions.” In other words, these boxes made it possible to mass-text and mass-call people. They are not cheap devices, costing in the thousands of dollars. And that’s before you get in the business of purchasing all those SIM cards.

The exact devices that the Secret Service found are sold by Ejoin for an eye-watering $3,730. Here’s a press image of one:

With devices like these, you can text someone at one number and immediately switch to another using the same cellular line, as if you changed area codes on the fly. Which sounds great for marketing, but also great for spam, and even better for harassment.

(It should be noted that Ejoin is not alone in selling these. I also spotted them being sold by Etross Telecom, OpenVox, and China Skyline Telecom. These are defiantly obscure but presumably have a use case.)

If you think these devices seem sketchy, apparently Alibaba does as well. If you look up messages on Alibaba for Ejoin Technology’s products, you get a generic logo, and this message that appears:

Due to the website’s compliance with specific regulations or policies in China, product information is no longer publicly displayed, but purchasing or payment operations can still be carried out. If you require detailed product information or link, please contact the sales department OR move to Ejointech offical Website.

So, if you buy these objects via Alibaba, you are literally buying a $3,700 device from a black box. On the plus side, going to Ejoin’s website, you can actually see screenshots of the tech in action:

In this context, these are basically spam machines, and whoever ran this network—whether a state actor or a criminal scheme—had dozens of them, each costing the price of a high-end laptop. The SIM cards themselves probably cost like $5-$10 a piece, maybe more, which means that just filling them up with cards likely cost thousands more. Plus, there’s the manual labor of it all. 256 SIM cards don’t put themselves into a SIMbank.

(Side note: When I searched for information on how to buy bulk SIM cards, one of the first sites that came up was a black-hat hacking forum in which a user asked the very same question. Which, to my friends in the black-hat hacking world, hello.)

Now, to be clear, there are some legitimate reasons for users to have them, particularly for testing and quality assurance across networks. (Say, if you’re concerned that your app might work differently on Verizon than it might on AT&T or T-Mobile, or if you’re doing a lot of edge computing. Perhaps a legitimate VoIP company has a few for whatever reason.) And I did find a user on Medium who posted why they built a SIM bank solution for their marketing team. But illegitimate use cases appear to dwarf the legitimate ones, at least in terms of public attention.

The case in New York is far from unique. Earlier this year, Interpol broke up a SIM bank fraud scheme in South Africa that involved 40 people and more than 1,000 cards. The cards were used to reroute international traffic as local traffic to make the calls look legitimate. And a spate of cases both targeting and based in India have emerged in recent months.

(By the way, if you find this topic interesting, you might want to check out the Indian cybersecurity news outlet The 420, which appears to be on top of this.)

Beyond the sheer scope of SIM cards that the network had, the fact that the Secret Service uncovered the network around New York City is perhaps the most interesting part. It suggests that we might see more tricks like this in the future.

Anyway, if you see one of these boxes lying around somewhere, filled to the brim with SIMs, odds are you might be in the vicinity of something sketchy. (One has to wonder if the rise of eSIMs is designed to make these products obsolete.)

As criminal as they might be depending on the situation, they admittedly look cool.