Article ID: 127799, created on Dec 18, 2015, last review on Dec 18, 2015

  • Applies to:
  • Plesk 12.5 for Windows


After removing of ModSecurity all sites are showing 503 Service Unavailable error.


ModSecurity was not properly removed


  1. Remove ModSecurity from Modules list in IIS Manager > <Hostname> > Modules

  2. Ensure that applicationHost.config file does not contain references to ModSecurityIIS.dll

    cmd.exe /c "findstr  ModSecurityIIS.dll "%systemroot%\system32\inetsrv\config\applicationHost.config""

In case if the file contains these entries:

  1. Backup applicationHost.config

    cd %systemroot%\system32\inetsrv\config\
    copy applicationHost.config applicationHost.config.original
  2. Edit applicationHost.config with notepad.exe and remove all entries that contain ModSecurityIIS.dll
    Note: Do not use WordPad.

Search Words

IIS ModSecurity


IIS ModSecurity

ModSecurity 503 error

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