Why Link Farms (used to) Work
I tripped over a reference to an interesting paper on PageRank hacking while looking at some unrelated rumors at Ian McAllister’s blog. The undated paper is titled “Faults of PageRank / Something is Wrong with Google’s Mathematical Model”, by Hillel Tal-Ezer, a professor at the Academic College of Tel-Aviv Yaffo.
It points out a fault in Google’s PageRank algorithm that causes ’sink’ pages that are not strongly connected to the main web graph to have an unrealistic importance. The author then goes on to explain a new algorithm with the same complexity of the original PageRank algorithm that solves this problem.
After a quick read through this, it appears to describe one of the techniques that had been popular among some search engine optimizers a while back, in which link farms would be constructed pointing at a single page with no outbound links, in an effort to artificially raise the target page’s search ranking.
This technique is less effective now than in the past, because Google has continued to update its indexing and ranking algorithms in response to the success of link spam and other ranking manipulation. Analysis of link patterns (SpamRank, link mass) and site reputation (Hilltop) can substantially reduce the effect described here. Nonetheless, it’s nice to see a quantitative description of the problem.
See also: A reading list on PageRank and Search Algorithms
Tags: search, google, algorithms, pagerank, spam, hacking, seo
