DOS Attack on Server!
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Thread: DOS Attack on Server!

  1. #1
    Did someone said Pizza :) FanacooL's Avatar
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    Unhappy DOS Attack on Server!

    Hi!
    We have hosted an application on our server which gets accessed across the globe. Everything works fine for years but suddenly from last 2 weeks we face issue that users complaint server not responding. Upon checking our Cisco ASA we identified numerous attempts from IP's from CHINA that tries to connect to our Server. As a result our users unable to access the server, although time to time we are blocking the unknown pools using ASA but yet the Attacks keep on coming from different sources.

    Current Network Setup is As following: -

    ISP => Cisco ASA => SQL Server
    ||
    DC
    ||
    LAN

    OS = Windows 2003 (Also running MS ISA 2004)

    Our application get accessed from different source machines so we can't directly block all unknown source IP for this particular application using Cisco ASA.

    Any suggestion how can we block/minimize these DOS attacks?
    One machine can do the work of fifty ordinary men. No machine can do the work of one extraordinary man!

  2. #2
    Gonzo District BOFH westin's Avatar
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    Block all of China. :-P
    \"Those of us that had been up all night were in no mood for coffee and donuts, we wanted strong drink.\"

    -HST

  3. #3
    Did someone said Pizza :) FanacooL's Avatar
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    I wish this could have been possible.
    One machine can do the work of fifty ordinary men. No machine can do the work of one extraordinary man!

  4. #4
    Antionline's Security Dude instronics's Avatar
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    Quote Originally Posted by FanacooL View Post
    I wish this could have been possible.
    Maybe this will help you to block some

    For Web server's .htaccess blocklists go here:
    Code:
    http://www.wizcrafts.net/chinese-blocklist.html
    and for firewall/iptables/other formats of ip addresses go here:
    Code:
    http://www.wizcrafts.net/chinese-iptables-blocklist.html
    In addition to this, you can monitor these pages for changes in IP addresses and get the alerts via emails by using this:
    Code:
    http://www.changedetection.com/
    NOTE: The links i have provided are mainly against Asian addresses. If you go to the homepage of wizcrafts you have other countries too such as nigeria etc....

    If my memory is correct then i got these links/ideas from Nihil some time ago, so special thanks to goto Nihil.

    Cheers everyone.
    Ubuntu-: Means in African : "Im too dumb to use Slackware"

  5. #5
    Junior Member
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    You should look into fail2ban alternatives for Windows, there's got to be something out there like that.

  6. #6
    Did someone said Pizza :) FanacooL's Avatar
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    @instronics
    Its quite helpful Thanks.
    One machine can do the work of fifty ordinary men. No machine can do the work of one extraordinary man!

  7. #7
    Just Another Geek
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    You need to stop it before it hits your webserver.

    http://www.networkstraining.com/conf...tect-from-dos/
    Oliver's Law:
    Experience is something you don't get until just after you need it.

  8. #8
    Junior Member
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    You have several options with you ASA, you can set connection limits to that server, so when it reaches a high volume of hits it will start shunning those connections and prevent an overload on that server. Another option is to just block that ip or range that is hitting your server.

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