Disclaimer: No illegal activity is condoned in this post. The legality of the described activity varies from country to country.
I remember in the early 00's, when peer to peer file sharing was booming. I would download music from Kazaa. After a few months of happy piracy, I would start getting these music files that were fine for the first 15 seconds, but then started making a horrible buzzing sound for the rest of the track. My 13 year old self speculated that these files may have been intentionally seeded in great numbers by the RIAA or someone like that, in an attempt to flood the network and thus make it useless. They seemed the most likely candidate with means, motive and opportunity to seed so many files on such a large scale. It didn't take long before "verified" file sharing sites started being a popular starting place for p2p.
Recently, on sites like The Pirate Bay, I've seen that there are files that have a huge amount of seeders, but no comments, and they were typically all posted less than a day ago. Typically, the same user has posted many different files like that, and they all have a huge amount of seeders. I have downloaded many such torrents. (Running them in virtual machines for experimental purposes.) Quite often, I have found them to be packed with malware and viruses. (Not just the keygens, which often give false positives, but actual malware that flood your system with advertisements, etc). In other cases it may just be a version of a game that appears to work, but promptly crashes 10% into it, or something like that.
In a normal situation, one would expect the best, cleanest and most functioning version of a program to get the most seeders, as that one would have the best comments under it, and be shared around and accessed the most. Yet that is often not the case. Usually you have to go quite a bit down the list to actually find a good torrent with good comments.
Who are regularly reuploading these bad/infected versions of software, and seeding them on a large scale? Who has the means, motive and opportunity to do this?
One thing that comes to mind is botnets who just want to distribute adware, and thus make money. That's quite possible. But that doesn't explain versions of software that simply don't work, or appear to work at first, but malfunction after a short time (no adware).
If I was Adobe, or Rockstar Games, or Microsoft or someone like that, I would recognize what an incredible blow online piracy is to my company's revenue. These companies' income would increase immensely if online piracy disappeared or was greatly reduced. And actually, trying to find pirated versions of software and instead getting all these fakes and malware on top of the list, is a great deterrent that probably stops lots of people from pirating, leading many of them to buy the software instead.
If I was these companies, I would find uploading and seeding this stuff on a large scale quite a good idea, in an attempt to combat piracy of the software I sell.
But, would it be illegal of them to do so? Sure, they are only punishing people who are already breaking the law. (Unless someone was in a country that hasn't banned piracy), but would it still be illegal for a company to distribute viruses in that way? I mean, the viruses may spread further, infecting innocent people's computers.
Is there any evidence that software companies actually engage in this form of piracy prevention? You may include instances where a company has paid a proxy entity to engage in the activity for them.