Verified-Sender: Improving Safe Message Detection in SMiShing

SMS phishing poses a significant threat. Small mobile displays lack the sender’s address transparency. A signal nudge in the representation of a checkmark shield icon is proposed as a verified-sender cue to aid in the identification of safe messages. This experiment examines whether the presence of this nudge impacts users’ ability to distinguish between safe and malicious messages. Our findings suggest that the nudge significantly improved the accuracy of safe message detection by 10%, while the accuracy of malicious message detection remained unchanged. The nudge serves as a positive verified-sender cue that helps users confirm safe messages, but, on its own, does not help users reject phishing. Additionally, no detectable increase in perceived workload (NASA-TLX) was found. The implemented nudge does not function as a phishing defense. Instead, it helps users recognize legitimate messages as safe without any spillover resistance to malicious messages.