The dependence of modern societies on electric energy is ever increasing by the emergence of smart cities and electric vehicles. This is while unprecedented number of cyber-physical hazards are threatening the integrity and availability of the power grid on a daily basis. On one hand, physical integrity of power systems is under threat by more frequent natural disasters and intentional attacks. On the other hand, the cyber vulnerability of power grids is on the rise by the emergence of smart grid technologies. This underlines an imminent need for the modeling and examination of power grid vulnerabilities to cyber-physical attacks. This paper examines the vulnerability of the communication-assisted protection schemes like permissive overreaching transfer trip to cyberattacks using a co-simulation platform. The simulation results show that the transient angle stability of power systems can be jeopardized by cyberattacks on the communication-assisted protection schemes. To address this vulnerability, two physical solutions including the deployment of communication channel redundancy, and a more advanced communicated-assisted protection scheme, i.e., directional comparison unblocking scheme (DCUB), are considered and tested. The proposed solutions address the vulnerability of the communication-assisted protection schemes to distributed denial of service attack to some extent. Yet, the simulation results show the vulnerability of the proposed solutions to sophisticated cyberattacks like false data injection attacks. This highlights the need for the development of cyber-based solutions for communication channel monitoring.