Hi would like to know how google can know (if it possible) that somebody is doing 3 way link exchange. Thanks for your help
i dint understand what you want to say about 3 way .. that u can have adds o ther companies also but not on same page where google adds are there ... means one site 3 or 4 adsense companies .. shivaprem webmaster
The answer is that most of the time they can't detect it. Sometimes they can detect interlinked networks of sites but this can be a good thing if the sites are related.
I don't think SE can detect it as long as diff IPs. 3 way is basically 3 one way links among the 3 web sites, so I don't think SE can know that.
3-way linking is when you link some of your sites to some sites of somebody else, and that other person link to other site of yours, right? They can detect it, because they know which sites are yours and which site are theirs. Technically speaking (algorithmicaly) they can group sites by owner into one node and do "find the cycle". For finding cycles in the graph they don't performs BFS or DFS since better algorithms have appear for large graphs.
Hm, diffcult, but they might look at link relevancy. Apart from TrustRank algorithm they develop statistical approaches to detect suspicious link behaviour. I don't know details about those statistical approaches but if you fit in it, they could detect it.
They wouldn't know -- to the best of my knowledge -- unless all the sites are using some 3-way link building network service, and the system leaves some footprints that SEs can detect. E.g. a "powered by super 3-way link building network service" notice, or similar. Also, there's TrustRank. Humans can detect things spiders can't. Warkot