Audio conference call security:

*Use the passcode assigned to your conference call at the time the reservation is made. This will prevent callers without the proper passcode from being admitted to the call.

*Protect the passcode and any other account information associated with the call. This means limiting who receives the information. Also get in the habit of shredding any documents that contain this information.

*Be sure to enable entry and exits tones to notify you when a participant joins or leaves the call.

*Require that participants identify themselves when joining the conference call and also take roll before commencing the conference.

*Lock the conference call so no one else can join it once begun.

*Disconnect all lines to the call at the end of the call to make certain there aren’t any side discussions after the conference has ended.

*Get in the habit of changing the call-in numbers and passcodes on a regular basis

From: http://www.conferencecallogy.com/Conference-Call-Security.html