A plug-in module, which, in combination with a host module, prevents unauthorized copying—like screen captures, screenshots, or screen recordings—of the streaming content provided to a participant in an online content-sharing session via an Instant Messenger (IM) service. The plug-in module may be a part of an IM application running on the participant's system or the host module may transmit a self-installing plug-in module to the participant's system upon receiving an indication that a user is hosting the online session. The plug-in module provides kernel-specific interface of the participant system's Operating System (OS) to the host module, which, then sends an OS-specific instruction to the plug-in module to trigger the OS to disable or control the copying of the streaming content as specified in a privacy preference received from the user hosting the online session. In this manner, sensitive and critical business data may be conveniently and securely shared online.