You should protect the privacy of your own employees as well as the confidentiality of sensitive company and customer information by implementing a policy banning employees from using their personal cell phones or other recording devices to tape conversations in the workplace without authorization. If you already have such policy in place then now would be the time to take disciplinary action.
Take a look at the tools listed below that will help you navigate this situation.
Can You Fire an Employee for Secretly Recording Work Conversations? – Quiz
Employees Use of Recording Devices in the Workplace Policy
Surreptitious Recordings Of Colleagues At Work May Be Cause For Dismissal