Copied from MetaWikiPedia:Wiki_Spam
What is wiki spam?
WikiSpam is the wiki equivalent of e-mail and blog spam. Wiki spammers edit pages to include advertising links to their sites. Spam links appear as full URLS (e.g. http://example.com), as named links with a spam keyword, or as numbered links (e.g. ). Often a spammer will completely replace the legitimate content of a page with their spam, and may add many different links, with a range of URLS and keywords.
Why are the spammers doing this?
Spammers are not really hoping that you will click on their links, although if you do they are likely to be happier. Their actual goal is to improve their position in Google searches. Wikis are characterized by their open access and willingness to let anyone edit pages. Google measures its PageRank based on links from one site to another, weighted by the PageRank of the site linking to the other. Wikis are PageRank machines, being both massively linked and with hundreds or thousands of pages. These two factors, openness and PageRank, make wikis a tempting target for spam attacks.
Does it work?
Probably not. All outbound links on Wikipedia:MediaWiki sites are marked by default with an attribute telling Google and other search engines not to count the link for page rank. If a search engine chooses to use these marked outbound links for page rank, it is expected also to be smart enough to recognize the difference between a link to site mentioned on many pages here and elsewhere (such as wunderland.com) and a spam site that nobody intentionally links to without complaining about spam. But spammers don't care whether it works or not. The spammers have a botnet of compromised computers. The botnet puts their text on hundreds of wikis and thousands of blog comments every few minutes at essentially no cost to the spammers. If they want to spam us, we will be spammed.
How to remove spam
Anyone who can edit the wiki can manually revert abusive edits. MediaWiki (and all good wiki software) allows you to overwrite the current (spammed, vandalized, or otherwise unsuitable) version of a page with an older version.
- Click "History" tab at the top of a page. ("Page history" may be elsewhere in some skins.)
- Take the time to find to the latest version without the vandalism; there may be multiple vandal edits. Take note of whose edit was the last before the damage.
- Click on the timestamp link of the revision you want to recover ("cur" and "last" don't work for this). This will take you to a page with the text of the old revision.
- Click "Edit" tab at the top. You'll get a warning about editing an out-of-date revision.
- Add a summary, such as "revert spam to latest by GoodWikiUser", and click the "Save" button.
When you revert a change, the previous spammed version of the page is still available under the "History" link. As a user, there is nothing you can do about this. It has to be this way, because otherwise vandals could do malicious reverting of changes.
If somebody else saves an edit to the page just before the reversion is saved, their edits will generally be deleted. It's good to check the change history again immediately after a reversion, to catch this occurrence.
Other action users can take
Create pages to explain the problem
Create a page called [[Project:WikiSpam]] or [[Project:Wiki Spam]] to explain the problem (why not steal the top three sections from this page?), and report incidents of spamming.
Create a page called [[LinkingPolicy]] or [[Linking Policy]] to clarify what kind of linking is encouraged/discouraged on your wiki, and what constitutes Spam.
Steal spammer's rankings with chongqed.org links
http://www.chongqed.org is a fighting wiki spam by building a database of spammers and also their favourite spamming keywords. They are asking the wiki community to link to this database with keywords which the spammer was trying to gain google rank on. This is an easy way for everyone to fight back against this menace. Place the links somewhere on your wiki, where it is tidy to do so (e.g. on a spam reporting page)