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Access Blocked
    Keywords: SL description

Sensei's Library tries to protect itself from dumb mirroring scripts that issue some thousand requests within minutes bringing our server to its knees. Three measures have been taken:

  1. checking for referrer information
  2. hidden trap link
  3. limiting requests/minute

Referrer information

A first measure is to block access to any function other than viewing a page, if there is no referrer information present. What does this mean?

Every time you click on a link your browser sends a request to our server to get the desired page and pictures. This request not only contains the pagename which you would like to see, but also which page you are coming from (referrer information).

However, mirroring scripts don't send this information. So checking for the referrer information is an easy way to distinguish between scripts and regular browsers.

If there is no referrer information then everything but viewing a page is blocked (e.g. diff, edit, save, search, pageinfo, ...).

If you get the "AccessBlocked" message as a regular user than either you are not using a standard browser, or have configured your browser in a way to not send the referrer information, or a proxy you are using is removing this information. Solution: change your settings or set a cookie (the referrer check is circumvented if you have the SLPrefs cookie set).

As the referrer information has to originate from within SL it is no longer possible to link to diff, pageinfo, etc. from other websites. Note: you can still link to pages themselves.

Hidden trap link

As a second measure, there's a trap link on the pages for scripts to follow if they don't obey the robots.txt file. Users should not normally be able to see this link. (You can see it in the source, but don't try it out or your address will be blocked for 48 hours. Really. We mean it.)

Limit requests/minute

Some scripts issue many requests per minute. We now enforce a limit of 35 requests/minute. Any IP issuing more requests is first warned and subsequently blocked for 6 hours.

If you are a regular user and got blocked by this, then send us an email. Maybe you should reconsider your browsing habits :o)


The above measures should shield SL from the most offensive scripts. What if you would still like to have a local copy of SL?

-> Download a ready packed snapshot at SLSnapshot.

See also: Why mirroring is bad.

Contact ArnoHollosi or MortenPahle if you have further questions.




This is a copy of the living page "Access Blocked" at Sensei's Library.
(C) the Authors, published under the OpenContent License V1.0.