Anonymous users should not be allowed to post external links

(English) This is an essay. It expresses the opinions and ideas of some Wikimedians but may not have wide support. This is not policy on Meta, but it may be a policy or guideline on other Wikimedia projects. Feel free to update this page as needed, or use the discussion page to propose major changes.

The following is a suggested technical solution to the problem of Wiki Spam. It is not available as an option in the MediaWiki software. It is only a proposal. For features which are actually available, see Anti-spam Features.

The Problem

As we probably all know, spam is a problem on wiki's. I am particularly active on one Wiki, the Fastmail Wiki, and although the extent of the problem is limited there, it's large enough to be considered bothersome.

On Meta I found (with pointers by user:Angela) several pages that propose solutions for this problem, for example Anonymous users should not be allowed to edit articles and Posting by anonymous users should be limited, but not banned. The main criticism on these suggestions seem to be that they go against the whole spirit of Wiki'ism, the free flow of information and all that. Anonymous editing is part of Wiki Culture and should not be forfeited in the battle against spam the critics say and I agree completely with that. A solution to the spam problem needs to be found, though.

Google has recently introduced the rel=nofollow tag. While the idea of instructing search engines to not consider links in wiki's to be 'valid' when it comes to calculating the relevance of the page being linked to sounds great initially, this too is not the solution. Wiki's, and especially WikiPedia, produce lots of high-quality external references. By adding rel=nofollow to all these external links lots of positive information about such pages might be lost. See also the discussion on Nofollow.

Pondering this I came to believe that a possible solution to this problem was to be found in subtle things that disrupt this flow as little as possible, while forming a large enough obstacle for spammers to mend their ways.

The Solution

See the title of this page. All spam that we have received on the Fastmail Wiki so far is very simple in nature: Anonymous user logs in, finds a seemingly random page, edits it by adding links to his spamvertized sites and saves it. The idea is probably being that such spam will either lead to direct clicks from visitors looking at the Wiki, or Google PageRank by generating lots of incoming links. Both of these require links to be made. The suggestion I make is simple: Anonymous users can edit all they want, but as soon as the Wiki encounters a link to an external site (Whether or not InterWiki links are external I leave open for discussion) the user will be displayed the Edit area again with a polite notification 'To post links to external websites, please register or log in'.

Should this suggestion be implemented my personal preference would be to make it enabled by default, but possible to disable. This way people who want to run a Wiki that is completely editable by anonymous users can have it their way, and people who want to implement this feature can do so. Perhaps an even better idea would be to have this as a permission that can be set on various usergroups. I dunno about all this; should this be implemented I'll leave it to those who know to decide how to do it.

Objections / Possible Objections

1. It won't solve the problem. Many automated wiki spam bots already know how to create accounts and login, then proceed to edit pages and add links under their created username. A lot of people have locked down their wikis such that any anonymous editing is disallowed, only to find that the spam still comes.
2. The CAPTCHA challenge required on each edit for non-autoconfirmed users adding URLs already defeats automation.
3. The ability to edit immediately without having to create an account can have a recruitment effect. Accordingly, disallowing it may hinder outreach.
4. Casual passerby edits done by mostly non-editing readers like typo fixes would not be done.
5. Vandalism and promotional edits from IP editors can be traced, which allows telling that, for example, they originate from a school or company. On the German Wikipedia, this allowed identifying promotional edits made from computers of Daimler (Mercedes-Benz)([1]) and the "CDU" political party([2]).
6. It is a shame to introduce any restrictions to anonymous editing. It may not seem all that important, but some non-technical users do not understand, or have the patience for the registration/login process. Allowing these non-technical users to contribute freely is something wikis are uniquely capable of. Must we allow Wiki Spam to spoil all of that?
7. Possibly a processing speed sacrifice: Parsing all content for external links (not only clickable, but also plaintext links) could slightly slow down MediaWiki. I am not too sure this is a valid argument, since there are already a quite a lot of regular expressions being parsed upon each edit, so one more (and with a pretty valid purpose) should not matter all that much.
8. Possibly difficult to implement: It could be that the internal structure of the script that handles posting an edit to the database does not allow for such checks. It would surprise me to hear that, but the possibility exists.
9. Possibly this can already be done: That would surprise me a lot, since I never found anything about it, but if it does please let me know ASAP!
10. It would interfere with editorial policies. Wikipedia requires editors to cite their sources, which is often a website. This policy would prevent anonymous editors from linking to their source, so other editors can easily verify it.