yes you can buy guns though mostly it's 3D printed shit where with every shot fired the chance that it blows up in your hand increases. There are some guns which are better quality but they are very probably tainted.
The darknet is lending itself extremely poorly for this type of transaction. Anonymity is exactly what I do not want when obtaining a weapon (yes even you tend to commit a crime with it). you may remain anonymous but the potential history of the gun certainly won't be and is traceable more accurately than any fingerprint.
The only reason why you might want to sell a gun there is to get rid of potential evidence while at the same time pin the crime on another person.
According to a study conducted by RAND Corporation, most firearm vendors on the darknet (59%) originated from the United States, but the combined revenue of European sales are 5 times higher than those of the US.
Most guns sold in Europe are coming via the South-West into Europe, usually from Russia, via Moldova, Serbia, Albania, etc. Small firearms are highly available in Europe if you know where to look. I very much doubt that the sale of all guns on the darknet is higher than 1% from all total trade. It's neither profitable nor practical to sell arms on the darknet.
Sure, they can trace the gun...but who cares? All they can do is trace it back to the guy who sold it to you. If you're intending to commit a crime with it, I don't see how that's problematic for you.
How does image recognition help with this? The gps data is right there in the JSON.
Also at the beginning of the article we see:
"Since users want to remain anonymous and criminals often use their own jargon, it is far more difficult to navigate and track the plans of cyber criminals."
So it is very handy that the JSON contains the uncensored urls, which saves us part of this trouble... not very clever.
That said, the article can be reduced to:
- they are using trained networks to classify images and make those tags searchable
- they are reading exif data from images and make that searchable
That's it. If it's a photo of pills hosted by some hidden services it's “illicit content” per their approach.