The algorithms used in GSM networks are known to be weak, and attackers can exploit them to perform various attacks, such as eavesdropping. However, 2G (GSM) networks are still widely used worldwide, especially by IoT devices, and as a fallback when networks utilising 4G and 5G technology are unavailable. Therefore, the security of GSM networks is still relevant today, and efforts should be made to ensure that these networks adhere to modern security standards. In this paper, we propose low-cost methods that can be used to determine the encryption algorithms employed by mobile operators in their GSM networks. We applied these methods to perform a case study, analysing the algorithms used by Estonian mobile operators. The results show that even in 2024, there are mobile operators who only support the A5/1 encryption algorithm to secure communication privacy for devices operating in their network, leaving these devices vulnerable to eavesdropping attacks.