Summary: I hate black hat SEO, because it proves to me that Google has so many vulnerabilities even today. It’s not as bad as it used to be, but spammers still rank really well on competitive key phrases using very dirty tactics. It’s worth knowing who is up to this and how it works.
Tip 1: For some reason, spammers don’t tend to pay much attention to site quality. I suppose it’s because it’s so easy to rank when you know how. Therefore look at domains which have bad web addresses like online-roulette-games-bonus.com. Spammers often run large numbers of domains at the same time and it’s sometimes a lottery as to which ones end up ranking.
Tip 2: Use tools like majestic or Ahrefs to look at the link profiles for these sites. Does the site have thousands of back links that came through very quickly? And are they relevant or not?
Tip 3: If the links are very strong and from irrelevant sites, there probably from networks like SAPE. Companies like SAPE crawl the Internet looking for domains which have vulnerabilities. If they can get into the website, they place a script in the site which then controls what links are placed from a central point. (Yes this is evil)
Tip 4: if you are using WordPress, it’s known for its vulnerabilities so update your plug-ins now! Also check your link profile to see that you’re not being spammed for some reason.