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Sysadmin DDOS attack, how to detect and prevent

Discussion in 'System Administration' started by ahmed, Jun 20, 2017.

  1. ahmed

    ahmed Member

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    Feb 21, 2017
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    Hello

    my website today was sluggish (loading time was 28 sec instead of 1 sec)

    was that a DDOS attack?
    How to confirm?

    or it was just normal server slowing due to other factors such as network congesion?
     
  2. eva2000

    eva2000 Administrator Staff Member

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    Brisbane, Australia
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    Nginx 1.13.x
    MariaDB 5.5
    First become familiar with tools and monitoring below

    CPU load optimal is 1.0 per cpu thread so 8 cpu thread normal = 8x1 = 8.0. 16 cpu server normal is 16x1 = 16.0

    so cpu load of 8 for
    • 2 cpu server = 8/2 = 4.0 load average
    • 4 cpu server = 8/4 = 2.0 load average
    • 8 cpu server = 8/8 = 1.0 load average
    When you type top command, hit number 1 to break down per cpu stats

    Centmin Mod is provided as is, so troubleshooting load issues is left to end user to do. However, there's many linux tools and scripts that can help you figure out what was causing the load and slowness issues and when.

    If you're providing info on this forum, more info might be helpful
    1. What version of Centmin Mod ? .08 stable or .09 beta ? If .09 beta when was it installed and when was last time you updated ?
    2. What's your VPS/Server hardware specifications ? cpu type ? memory available ? disk space ?
    3. Who's your web host ? Different hosts have different limits for server resource usage and some are more restrictive that others so it could just be their resource usage policy you tripped which may or may not be restrictive. If restrictive, then real solution would be finding a better web host. If not restrictive, then it's finding out what caused high cpu load.
    Tools and commands you will want to read up on and learn for basic system admin tasks and troubleshooting.
    Notes:
     
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  3. viralpoet

    viralpoet Member

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    I must admit I love the simplicity of the setup and install of monitorix