Quantum Key Distribution is an emerging technology for secure communication, based on quantum principles to ensure secure key exchange. However, in practical implementations, Quantum Key Distribution systems are susceptible to side-channel attack, i.e., Trojan Horse attack, where an eavesdropper injects external light into quantum devices to gain information about the protocol parameters. This work investigates the impact of the Trojan Horse attack on the performance of three well-known Quantum Key Distribution protocols, namely BB84, E91, and SARG04, under varying intensities of Trojan Horse attacks. This work has been carried out using IBM Qiskit, and the performance was analyzed in terms of Quantum Bit Error Rate and Secret Key Rate. The results show that each protocol exhibits different levels of susceptibility, with the BB84 and SARG04 protocols showing greater resilience, while E91 appears more sensitive to injected noise. These findings provide insights into protocol-specific vulnerabilities and assist in designing Quantum Key Distribution systems that can withstand advanced eavesdropping strategies.