The methods these unethical developers used are pretty classic black-hat tactics. For many years now, blackhat optimizers have used automated agents to insert keyworded textlinks into blog and forum comment areas and online guestbooks, pointing back to their sites in an effort to built PageRank. In addition, really old and crusty black hat techniques include keyword stuffing ” adding tons of keywords on a page in an effort to make the page relevant for words and phrases. Also, the bait-and-switch technique of allowing one page to get indexed by search engines while redirecting human users to a different URL is pretty well known.
In recent months, Google has apparently been working particularly industriously to penalize more sites that may be buying/selling links or which may be involved in various linking schemes. So much so, that theres been considerable talk about how some of the affected sites mayve been unfairly red-flagged by bad assumptions made by their algorithmic policing software. So, its disappointing that a network of egregious malware sites were able to effectively employ legacy black-hat tactics which ought tove been detectable earlier.