In this paper we propose a new mechanism to guarantees QoS during DOS attacks for IPTV networks, we introduce the concept of "video stream handoff" analogous to the "soft handoff" done in cellular networks, the idea is to initiate a selective video handoff procedure, either from the server side, when the DOS attack is detected, or from the user side when QoS degradation occurs. All of that should happen without interrupting the user (i.e. while the video is playing). We make use of the SIP protocol stack for signaling, QoS negotiation, and session management.