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Link Spam
Link spam
(also called
blog spam
or
comment spam) is a form of
spamming
or
Spamdexing
that recently became publicized most often when targeting
weblogs
(or blogs), but also affects
wikis
(where it is often called
wikispam), guestbooks, and online discussion boards. Any web application that displays
hyperlinks
submitted by visitors or the
referring URLs
of web visitors may be a target.
Adding links that point to the spammer's web site increases the
page rankings
for the site in the search engine
Google
. An increased page rank means the spammer's commercial site would be listed ahead of other sites for certain
Google
searches, increasing the number of potential visitors and paying customers2.
Link spamming originally appeared in internet
guestbooks
, where spammers repeatedly fill a guestbook with links to their own site and no relevant comment to increase search engine rankings. If an actual comment is given it is often just "cool page", "nice website", or keywords of the spammed link.
In
2003
, spammers began to take advantage of the open nature of comments in the
blogging
software like
Movable Type
by repeatedly placing comments to various blog posts that provided nothing more than a link to the spammer's commercial web site. Jay Allen created a free plugin, called MT-BlackList1, for the Movable Type weblog tool that attempts to alleviate this problem. Many current blog software now have methods of preventing or reducing the effect of blog spam.
Because of prevention improvements in blog software link spam is now increasingly concentrated on
wikis
around the
World Wide Web
including
Wikipedia
, the largest wiki on the Internet (see
[1] (http://en.wikipedia.org/wiki/Wikipedia:Spam)). Wiki spam sometimes only appears on a wiki's
sandbox page
, but is often found defacing multiple pages. This page3
lists
URLs
and
IP addresses
of offending wiki spammers.
Possible solutions
-
Recently Google
introduced an HTML attribute (http://www.google.com/googleblog/2005/01/preventing-comment-spam.html)
to prevent ranking credits. Search engines and weblog software already follow this convention.:
<a href="http://www.wiki.org/" rel="nofollow">Link</a>
-
Instead of displaying a direct hyperlink submitted by a visitor, a web application could display a link to a script on its own website that redirects to the correct
URL
. This will not prevent all spam since spammers do not always check for link redirection but has proven very effective. Redirecting links prevent Google from factoring the link in its
PageRank
algorithm for that site making the spam ineffective. An added benefit is that your redirection script can count how many people visit external URLs, but one drawback is the increased load on your website.
-
Idea: However, the script could also be client-side
JavaScript
. For example,
<a href="javascript:window.location.href='http://www.wiki.org'">Link</a>
would work as a link but not be picked up by Google. Moreover, the javascript could be more complicated to ensure that the link would never be picked up since it was
encoded
. For example,
<a href="javascript:redirectFunction('hfksksgjlsll')">Link</a>
where 'hfksksgjlsll' is an encoded
URL
that is decoded by the javascript
function
redirectFunction which presumably is stored in the
HEAD tag
of the page. A downside of this is that visitors who have disabled Javascript in their browser would be unable to follow the links.
-
This redirect can also be done via the
.htaccess file
in
Apache
, thus saving the load of a script.
-
Require the user to solve a
captcha
, preventing bots from submitting entries.
Retrieved from http://en.wikipedia.org/wiki/Link_spam
Reprinted from Wikipedia, The Free-Content Encyclopedia under the GNU Free Documentation License.
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