The story is about someone who uses advanced technology (think Batman) to steal trade secrets (food recipes, chemical ingredients, manufacturing processes) from other companies and uses them to create his own versions of the products which his company then sells at lower prices (or whatever he can do to benefit from the trade secrets). How long can this last before other companies start to notice someone's been stealing their trade secrets and what can he do to prevent being discovered or prosecuted or otherwise having his business stopped?
They'll notice as soon as he's actually moving enough goods to come to their attention or advertising into their markets. Companies with IP to protect tend to keep a close watch on such things, but not always so much in markets where they have no activity.
Avoiding legal issues is easy, all he has to do is be a Chinese national operating out of mainland China. It's been standard business process there for decades, hence the phrase "cheap Chinese knockoff", it's exactly that, a cheaper copy of a product, usually to lower build standards that comes out of China.
The main quirk of this being that often the original product is also made in China, sometimes in the same factory or even on the same production line.
Just before his first product comes out
Firstly, court has discovery so as soon as you're about to release a product, they can put an injunction on you and demand all confidential data. You then need to argue why they shouldn't see it. At best you'll have a court appointed expert comparing your product to their product.
This happens even if you didn't copy anything and even if the products are not alike. This happened to me several years back. We developed a product that was light years ahead of anything else on the market. Just as we were about the release, one competitor claimed we stole their design and demanded all our designs, source code and documents. We had to fight them despite being nothing alike. If we didn't they would have gotten everything.
Court isn't about justice, it's just as easily used as a weapon to kill off competition.
Your best bet is to sell the info off to a competitor and let them fight and leave your thief in peace.
They wouldn't have to fear much
"Trade secrets" fall into two broad categories: technological and, for lack of a better word, "cosmetic"
"Cosmetic" trade secrets derive their value not from the actual information that's being protected, but from intangible effects like brand recognition. Food and drink recipes, for example, are guarded so jealously because of the marketing effort that went into popularizing the specific recipe. Now, any major soda company can at least approximate the Coca-Cola recipe closely enough that a human consumer wouldn't be able to tell the difference. However, Coca-Cola can always claim that "it's not the real deal", and many would believe them. If, on the other hand, the official recipe were public knowledge, it would not take long for competitors to bring a provably identical product to market at a significantly lower price.
In cases like this, you don't gain much from stealing the recipes unless you use them in marketing, which would be rather obvoius unless done cleverly. So, if you absolutely want to avoid getting caught, skip this category altogether. Anonymously leaking data to the general public might work, though, and carry limited risk unless you get caught in the very act of stealing the data.
Technological trade secrets concern know-how and techniques that aren't common knowledge and can serve to improve your products or production processes. In order to remain secret, these have to be non-obvious (i.e. not easy to discern via reverse engineering, chemical analysis or by hiring your competitor's ex-employees), otherwise the know-how would quickly spread. Consider, for example, the code for an in-house toolchain, or the plans for a not-yet-released product. Stealing those would not only be profitable but, because customers don't interact with them directly, difficult to prove. Anything that allows the other company to keep the details secret can be used by yours as well.
Now, there will always be suspicion, there will be legal battles and patent trolling, but that's an issue regardless of whether any kind of industrial espionage has taken place. The legal system is just another weapon in any corporation's arsenal, and having an information advantage on your competition can only be beneficial.
[These are a common occurence in infosec - inspired from there]
He simply puts it on the internet. With no way to trace back to him. In the background, he keeps his production assembly almost ready, to just start producing at the right time, yet with enough delay, so that no fingers get pointed at him. Soon others may join, but he is first to market, so he kills the competition.
If there are large number of trade secrets, he chooses the top X he wants to use for himself, and be prepared for them. The rest, he just releases on the internet in the hope that someone else will pick it up, so as to confuse the owners.
what can he do to prevent being discovered or prosecuted?
So he does nothing like that. He goes on the offensive rather staying defensive.
...what can he do to prevent being discovered or prosecuted or otherwise having his business stopped?
Read about capacitor plague where the formula for making capacitors was infected with a fatal ingredient/process (or was it a vital, missing ingredient?). In this case, it took a few years for these faulty capacitors to self-destruct, and many millions became embedded into a broad range of electronic devices before discovery.
These stolen-formula capacitors were trademarked with bogus manufacturers to obscure the real maker. Was the manufacturer obscuring their identity because they feared reverse-engineering might trace to themselves? Or did they know that their product was inferior? It seems they've escaped (so far).
Look for products which haven't been fully trademarked or copyrighted, copyright and trademark the products, and then sue the companies for copying them.
It has long been a tradition of people to take other's work and then make them pay.
So, have them have contacts within the companies and hacking and such, and aggressively get copyrights and trademarks on their stolen tech. Then, if the company releases the products, they can sue them for either a licensing fee, or pull them off the market for stealing his product.
The thief would have to be on the lookout for a "honey pot" intended to trick them into either revealing that they breached security in an illegal manner, or to physically capture them.
Most companies are not going to publicly announce that their trade secret has been found out, since that reduces the value of their product. For example, suppose the exact formula of Coke was "stolen". There is no advantage to Coca-Cola in announcing to the world that competitor X has the exact same product, they would be better off to allow consumers' imagination to tell them that the product in a different color can and different logo is slightly "off".
A deliberately created incident could allow them to shame competitors who financed the exploit, get the thief to admit the info is stolen, or even to capture the invisible man or however your character is getting into secure areas and acquiring information.