WikiSpam is the wiki equivalent of e-mail and blog spam. The spammers simply edit wiki pages, either manually or via the use of software robots, to include advertising links to their sites. WikiSpam often appears as explicit links (e.g. http://example.com); as [bracketed] links, which sometimes are difficult to detect if a spammer replaces the URL in a pre-existing [bracketed] link with the spam link; and as numbered links (e.g. ).
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.
Anyone who can edit the wiki can manually fix vandalism as soon as it happens. To make this recovery process easier, UseModWiki allows you to overwrite the current (presumably vandalized) version of a page with an older version.
When you revert a change in a usemod wiki, the previous spammed version of the page is still available under the "View other revisions" 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. Sadly this old revision is still available for search engines bots to find, which means the spammer will still gain google rank even after their spam is removed, unless your wiki administrator has installed WikiPatches/RobotsMetaTag
If you are in the business of watching out for spam, you should set 'Show minor edits' in your 'Preferences', since some spammers will attempt to hide their spam this way (though only a few are smart enough to do this). It would be nice if spam and spam reverting edits could disappear as minor edits from 'RecentChanges' page, however it should be noted that ticking your revert as a 'minor edit' does not have this effect, it just hides the fact that you have reverted the spam (better not to).
Other action which any user can take:
Create pages to explain the problem
Create a page called [[WikiSpam]] or [[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)
Remote anti-spam bots
Advanced users might like to try running an anti-spam bot, to remotely clean up spam on a wiki. See the BannedContentBot discussion. Take care with this 'machine-gun' approach.
Banning an I.P. address
Note that many spammers can switch I.P. address at the drop of a hat, and so banning their I.P. address may not keep them out for long, but it is very easy, so worth a try.
Prevent old revisions being indexed by search engines
Unfortunately in the default install on usemod old revision pages are still available for search engines bots to find, which means spammers will still gain google rank even after their spam is removed by a user. There is a simple fix for this: WikiPatches/RobotsNoFollow. This has no blocking effect on spam, and will not deter spammers completely, since they are normally too stupid to realise that their spam is having no effect upon search engines, however it will help you a little bit. It has been observed that spammers find places to spam, by searching for existing spam, and so if you avoid indexing spam, they won't find you. It is also an important contribution which all usemod administrators should make to the wiki-wide antispam effort, helping to make spamming a less worthwhile activity.
More effective than banning I.P. addresses, you can ban particular URLs from being linked to. Normally this is implemented by defining a list of regular expressions which will match against spammer URLs, and prevent any such edits being accepted. Unfortunately this is not part of the default usemod install.
It isn't hard to implement content banning. It's just a variation on the banned ip/host code. See WikiPatches/BannedContent . Please try out this patch and give us specific code feedback on that page (currently the info applies to an old modified usemod installation)
You can share your blacklist entries, or even better, get automatic updates from a centralised blacklist such as http://blacklist.chongqed.org/ This can prevent a known spammer attacking your wiki even once.
Block open proxies
Blocking open proxies will help reduce the problem of WikiSpam, and other abusive editing on your wiki. However it can potentially block out legitimate users. See WikiPatches/OpenProxy
Baysian filtering to mark changes as spam
The patch WikiPatches/UseBogoSpamNotify will mark a changes on your RecentChanges list, as 'Spam' or 'Ham'. It uses baysian filtering techniques (as used in most good email spam blocking software). This only labels the edits. It relies on the wiki community to spot the labels in the recent changes list, and clean out the spam.
Edit rate limit
Currently there is no way to limit the rate at which people can edit your wiki. (Correct me if I'm wrong)
See also other discussions on:
There is a german translation of the first part of this text: [WikiSpam (german)]