Q: How can I block FTP users from taking down my Windows FTP server by filling up its disk space?

A: Since Windows 2000, Microsoft has included a disk quota utility in the Windows OS that you can use to enforce user disk space limits on the volumes used by your Windows FTP server. To set quotas, you must have Administrator rights, and the volume must be formatted with the NTFS file system. Disk quotas use NTFS’ file ownership feature, which automatically attaches the name of the creator of a file to each file created on the NTFS file system.

Disk quotas are independent of the folder location of the user's files within a volume. For example, if a user moves files from one folder to another on the same volume, his space usage won't change. If he copies files to a different folder on the same volume, his space usage will double.

            To set up a disk quota on, for example, a Windows 7 system, you must follow these steps:

  • Open Windows Explorer. Right-click the volume to which you want to apply quotas and click Properties.
  • In the Properties dialog box, click the Quota tab.
  • On the Quota properties dialog box, click the Show Quota Settings button.
  • In the Quota Settings for <volume_name> dialog box, check the Enable quota management box then click Apply. If you want all new users to have access to a limited amount of disk space, click Limit Disk Space To then type an amount of disk space. If you want a warning message to be displayed when a user is about to reach his quota limit, click Set Warning Level To then type an amount of disk space.
  • If you want to set custom disk quota for a given user, click the Quota Entries… button. This action will open a new management interface named Quota Entries for <volume_name>.  From this interface, you can then define disk quota limits for specific user accounts.
  • To set a disk quota limit, select New Quota Entry… from the Quota menu option and type the name of the user account for which you want to set a limit. In the Add New Quota Entry dialog box, select the Limit disk space to radio button and type a disk space limit (in the example of Figure 1, this is 1GB). Also, make sure that you set a warning level.

 From the “Quota Entries for <volume_name>” interface you can also easily export the quota settings for a given volume and import them into the quota settings for another volume. To do so, use the Export.. and Import… options in the Quota menu.

If you want to set up disk quotas from the command line, have a look at the fsutil.exe command line tool that's bundled with Windows OSs.

TAGS: Security
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