Programmable Logic Controllers (PLCs) drive industrial processes critical to society, for example, water treatment and distribution, electricity and fuel networks. Search engines, e.g., Shodan, have highlighted that PLCs are often left exposed to the Internet, one of the main reasons being the misconfigurations of security settings. This leads to the question - why do these misconfigurations occur and, specifically, whether usability of security controls plays a part. To date, the usability of configuring PLC security mechanisms has not been studied. We present the first investigation through a task based study and subsequent semi-structured interviews (N=19). We explore the usability of PLC connection configurations and two key security mechanisms (i.e., access levels and user administration). We find that the use of unfamiliar labels, layouts and misleading terminology exacerbates an already complex process of configuring security mechanisms. Our results uncover various misperceptions about the security controls and how design constraints, e.g., safety and lack of regular updates due to the long-term nature of such systems, provide significant challenges to the realization of modern HCI and usability principles. Based on these findings, we provide design recommendations to bring usable security in industrial settings at par with its IT counterpart.

翻译：可编程逻辑控制器（PLC）驱动着对社会至关重要的工业过程，例如水处理与分配、电力及燃料网络。搜索引擎（如Shodan）已揭示PLC常暴露于互联网中，其主要原因之一是安全设置的错误配置。这引出一个问题：为何会出现这些错误配置？特别是安全控制的可用性是否构成影响因素。迄今为止，配置PLC安全机制的可用性尚未得到研究。我们通过基于任务的实验及后续半结构化访谈（N=19）开展了首次系统性探究，重点考察PLC连接配置与两项关键安全机制（即访问级别和用户管理）的可用性。研究发现，陌生标签、界面布局及误导性术语的使用加剧了本就复杂的安全机制配置过程。实验结果揭示了用户对安全控制机制的多重误解，同时表明设计约束（例如安全性要求及此类系统长期运行导致的更新滞后）为实现现代人机交互与可用性原则带来重大挑战。基于这些发现，我们提出设计改进建议，旨在使工业环境中的可用性安全达到与信息技术领域相当的水平。