It is mostly a myth (and scare tactic invented by copyright trolls and encouraged by overzealous virus scanners) that pirated games are always riddled with viruses. They certainly can be, if you download them from untrustworthy sources, but if you're familiar with the actual piracy scene, you have to understand that trust is and always will be a huge part of it, ways to build trust are built into the community, that's why trust and reputation are valued higher than even the software itself. Those names embedded into the torrent names, the people and the release groups they come from, the sources where they're distributed, have meaning to the community, and this is why. Nobody's going to blow 20 years of reputation to try to sneak a virus into their keygen. All the virus scans that say "Virus detected! ALARM! ALARM!" on every keygen you download? If you look at the actual detection information about what it actually detected, and you dig deep enough through their obfuscated scary-severity-risks-wall-of-text, you'll find that in almost all cases, it's actually just a generic, non-specific detection of "tools associated with piracy or hacking" or something along those lines. They all have their own ways of spinning it, but in every case it's literally detecting the fact that it's a keygen, and saying "that's scary! you won't want pirated illegal software on your computer right?! Don't worry, I, your noble antivirus program will helpfully delete it for you!"
It's not as scary as you think, they just want you to think it is, because it helps drive people back to paying for their software. It's classic FUD tactics and they're all part of it. Antivirus companies are part of the same racket, they want you paying for their software too.