Unveiling the Security Risks in Default Wi-Fi Passwords of Consumer-Grade Routers

With the increasing prevalence of mobile devices, wireless LANs, which allow network access without physical connections, have become widely used. Wi-Fi is particularly prevalent among wireless LANs, with a household Wi-Fi router adoption rate of approximately 89% and over 90% adoption in hospitals and schools in Japan. While Wi-Fi routers offer security features such as encryption and authentication, improperly configured or managed routers pose risks of eavesdropping and misuse by malicious actors. Previous studies have highlighted the risks of using vulnerable encryption protocols, such as WEP, and free public Wi-Fi services. However, the risks associated with default SSIDs and passwords on Wi-Fi routers remain largely unexplored. This study investigated the guessability of default Wi-Fi passwords across 44 consumer-grade Wi-Fi routers from 11 vendors commonly distributed in Japan. Our findings revealed that in 30 models from six vendors, default Wi-Fi passwords were generated using specific algorithms, making them vulnerable to being guessed by malicious actors. Based on the findings, we summarize the common pitfalls that product vendors often encounter when generating default Wi-Fi passwords. Additionally, we conducted a field survey across five locations in Tokyo, Japan to assess the prevalence and risk of Wi-Fi routers still operating with default settings.