3月24号Google的一项新专利获批，是关于判断超链作弊的办法。不禁感慨一下，这是黑帽SEOer时至今日多么常用的一个方法呀。但是鉴于这项专利是在2004年8月提交的，可以认为Google早就在内部采用这种方式执行检查超过5年以上了，所以对于指导我们的实践工作，没有太多新的价值。

专利里主要提到两种链接作弊模式：
       一类是Link Farm即我们常说的链接农场（often composed of many low PR pages pointing to a single site，也就是利用大量低PR的页面指向目标作弊页），这个方式常见于博客群建和留言群发；
   一类是Clique attack即站群策略（often composed of many high value sites linking amongst themselves, but not outside the ring,也就是一些高PR的站点之间互相链接，但是很少导出除去这个圈子以外站点的链接）。

我把专利声明的摘要内容贴一下：
        Methods for facilitating the identification of link spamming in a linked database include calculating a spam likelihood value for nodes in a directed graph of linked nodes are disclosed. The spam likelihood value is computed from an importance of the node and a derivative value of the importance function with respect to a coupling factor. The likelihood that the node's importance is inflated by link spam is estimated by calculating the ratio of the magnitude of the derivative value for the node to the rank for the node. Alternatively, the spam likelihood may be computed directly from a component of the principal eigenvector of A evaluated at two values of the parameter c. The normalized derivative value can also be used to provide an order of importance in a list of nodes.

另外三个相关的延伸阅读：
Ranking search results by reranking the results based on local inter-connectivity
Authoritative Sources in a Hyperlinked Environment
Hilltop: A Search Engine based on Expert Documents