You can take steps to ensure that MMR is accessible only to Horizon Client systems that have sufficient resources to handle local multimedia decoding and that are connected to Horizon on a secure network.
By default, the global policy Multimedia redirection (MMR) is set to Deny.
To use MMR, you must explicitly set this value to Allow.
To control access to MMR, you can enable or disable the Multimedia redirection (MMR) policy globally, for individual desktop pools, or for specific users.
For instructions for setting global policies, see Horizon Policies.