What is Spam mass?

Spam mass is defined as "the measure of the impact of link spamming on a page's ranking." The concept was developed by Zoltán Gyöngyi and Hector Garcia-Molina of Stanford University in association with Pavel Berkhin and Jan Pedersen of Yahoo!. This paper expands upon their proposed TrustRank methodology.

The researchers developed a good core and a bad core of selected Web documents from which they measured spam mass across a collection of documents. Two types of measurements, absolute mass and relative mass, are used to compare groups of documents. The higher the mass measurements, the more likely the documents are to be equivalent to spam.