Black hat SEO used to work in the early days of search engine optimization, so much so that many websites with substandard content rose to high ranking by pulling all sorts of tricks.
Most of those tricks used nowadays will land you in the sandbox.
That place where Google puts naughty websites.
The list of things that you should avoid in your off page SEO activities is not only long but growing quickly too.
It has become a veritable minefield, and every wrong step means your business will suffer.