Security Assessment and Evaluation of VPNs: A Comprehensive Survey. - Haider Abbas; Naina Emmanuel; Muhammad Faisal Amjad; Tahreem Yaqoob; Mohammed Atiquzzaman; Zafar Iqbal; Narmeen Shafqat; Waleed Bin Shahid; Ali Tanveer; Umer Ashfaq (ACM Comput. Surv., 2023)