  Web spam refers to some techniques, which try to manipulate search engine
ranking algorithms in order to raise web page position in search engine
results. In the best case, spammers encourage viewers to visit their sites, and
provide undeserved advertisement gains to the page owner. In the worst case,
they use malicious contents in their pages and try to install malware on the
victims machine. Spammers use three kinds of spamming techniques to get higher
score in ranking. These techniques are Link based techniques, hiding techniques
and content-based techniques. Existing spam pages cause distrust to search
engine results. This not only wastes the time of visitors, but also wastes lots
of search engine resources. Hence spam detection methods have been proposed as
a solution for web spam in order to reduce negative effects of spam pages.
Experimental results show that some of these techniques are working well and
can find spam pages more accurate than the others. This paper classifies web
spam techniques and the related detection methods.
