The answer to that question is a bit tricky since the website booter service for hire is problematic. Something is shady if an IP stresser service provider is hiding their identities and offering anonymous payment methods. That's how they can be untraceable from law enforcers if any investigations are to undergo. Of course, if a company tests its own network infrastructure by launching coordinated DDoS attacks on itself, that's perfectly legal. But if such an attack is launched against a third party with malicious intent is undoubtedly illegal in most countries.