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    • CommentRowNumber1.
    • CommentAuthorAndrew Stacey
    • CommentTimeJan 14th 2010

    Someone has effectively launched a 'denial of service' attack against the nLab. It brought it down yesterday and it's happening again now.

    While technically this is an attack, the specifics make me think that it is an attack-by-accident: namely someone is doing something by mistake that is causing the 'denial of service'.

    In short, a DoS (denial of service) attack occurs when something floods the webserver with so many requests that it can't handle them all at once and effectively locks everyone out. What seems to be happening here is that something is trying to download every single page on the nLab. That's EVERY SINGLE PAGE in case you missed it. Including every revision.

    That's EVERY REVISION. There's TWENTY-THREE THOUSAND of those.

    Sorry for the shouting.

    There's not a lot I can do about this, except shut down the server and hope that whoever is doing this goes away. I can block the IP, I can take down just the virtual host that these requests are going to, but that doesn't stop the requests coming in. And each request that comes in, has to be dealt with even if it's just to say "Go away". So that takes up time, and the shear number of requests means that it still floods the system.

    What makes me think that this is an attack-by-accident is that it is coming from one specific IP, both today and yesterday, and that IP is attached (it seems) to a university! It is:

    134.176.68.5 fbzelangenhorst.zmi.uni-giessen.de

    If you recognise any of that, please contact me!

    In the meantime, I have blocked that IP. At the moment, ncatlab.org is down. The machine is running absolutely fine, and the other aliases should work (www.ncatlab.org and nlab.mathforge.org) but since they all point to the same place, someone flooding ncatlab.org also floods the other two.

    • CommentRowNumber2.
    • CommentAuthorAndrew Stacey
    • CommentTimeJan 14th 2010

    Right, it wasn't going away so I've blocked that IP at an even lower level - it doesn't even reach the web server at all. In fact, as far as 134.176.68.5 is concerned, the nlab no longer exists.

    For the rest of us, the nLab seems to be back.

    • CommentRowNumber3.
    • CommentAuthorUrs
    • CommentTimeJan 14th 2010
    I talked about this with Andrew behind the scenes. It seems that the requests are coming from the media sociology department in Giessen, Germany, where the people work whose conference I mentioned here. This group studies the usage of new electronic media in science, and the nCafe and the nLab are among their objects of study.

    I have contacted them now and notified them that whatever they did, it happened to be hurting our server. As soon as I hear back; I'll let you know.
    • CommentRowNumber4.
    • CommentAuthorzskoda
    • CommentTimeJan 14th 2010

    Urs gets a brown belt in detective business :)

    • CommentRowNumber5.
    • CommentAuthorHarry Gindi
    • CommentTimeJan 14th 2010
    I thought that there were methods to block classical denial of service attacks, and that's why DDOS attacks are so important.
    • CommentRowNumber6.
    • CommentAuthorUrs
    • CommentTimeJan 14th 2010
    I have heard back from somebody now. The computer having caused the problem seems to be indeed one of theirs, and that person apologizes and promises to check what may have happened.
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