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.

Undocumented immigrants in the United States face risks of discrimination, surveillance, and deportation. We investigate their technology use, risk perceptions, and protective strategies relating to their vulnerability. Through semi-structured interviews with Latinx undocumented immigrants, we find that while participants act to address offline threats, this vigilance does not translate to their online activities. Their technology use is shaped by needs and benefits rather than risk perceptions. While our participants are concerned about identity theft and privacy generally, and some raise concerns about online harassment, their understanding of government surveillance risks is vague and met with resignation. We identify tensions among self-expression, group privacy, and self-censorship related to their immigration status, as well as strong trust in service providers. Our findings have implications for digital literacy education, privacy and security interfaces, and technology design in general. Even minor design decisions can substantially affect exposure risks and well-being for such vulnerable communities.