The Annoying, the Disturbing, and the Weird: Challenges with Phone Numbers as Identifiers and Phone Number Recycling

Abstract

Phone numbers are intimately connected to our digital lives. People are increasingly required to disclose their phone number in digital spaces, both commercial and personal. While convenient for companies, the pervasive use of phone numbers as user identifiers also poses privacy, security, and access risks for individuals. In order to understand these risks, we present findings from a qualitative online elicitation study with 195 participants about their negative experiences with phone numbers, the consequences they faced, and how those consequences impacted their behavior. Our participants frequently reported experiencing phone number recycling, unwanted exposure, and temporary loss of access to a phone number. Resulting consequences they faced included harassment, account access problems, and privacy invasions. Based on our findings, we discuss service providers’ faulty assumptions in the use of phone numbers as user identifiers, problems arising from phone number recycling, and provide design and public policy recommendations for mitigating these issues with phone numbers.