How to disconnect idle SFTP users?

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http://serverfault.com – I have a SFTP server, where clients connect every minute to exchange files. There are few clients who connect and then dont disconnect resulting in a lot of connections over a period of time. This is choking up the CPU. I have set ClientAliveInterval and ClientAliveCountMax in sshd_config which disconnects idle ssh connection after a certain period, but id doesnt seem to disconnect the idle sftp connections. How do I force idle sftp connections to disconnect? (HowTos)