Smishing is a form of phishing that uses mobile text messages (SMS) to deceive victims into providing sensitive information, clicking malicious links, or downloading malware. The term is a portmanteau of "SMS" and "phishing." This attack vector directly corresponds to the scenario of receiving an unsolicited text message on a mobile device as described in the question. The goal is to exploit the user's trust in text messaging to execute the attack.

A. Impersonation: This is a general technique where an attacker pretends to be a trusted entity. While used in smishing, it is not the specific term for an attack via text message.

B. Vishing: This attack uses voice communication (voice phishing), such as phone calls or voicemails, to trick users, not text messages.

C. Spear phishing: This refers to a highly targeted phishing attack aimed at a specific individual or organization, regardless of the medium (though typically email). The defining characteristic is targeting, not the use of text messages.

1. National Institute of Standards and Technology (NIST). (n.d.). Smishing. In Computer Security Resource Center Glossary. Retrieved from https://csrc.nist.gov/glossary/term/smishing

Definition: "A technique that uses text messages (SMS) to trick users into taking an immediate action

such as clicking a link to a fraudulent website

calling a fraudulent number

or downloading a malicious application."

2. National Institute of Standards and Technology (NIST). (n.d.). Vishing. In Computer Security Resource Center Glossary. Retrieved from https://csrc.nist.gov/glossary/term/vishing

Definition: "A type of phishing attack that is conducted by phone."

3. National Institute of Standards and Technology (NIST). (n.d.). Spear Phishing. In Computer Security Resource Center Glossary. Retrieved from https://csrc.nist.gov/glossary/term/spearphishing

Definition: "A targeted phishing attack that is customized for a specific organization or individual."

4. Cybersecurity and Infrastructure Security Agency (CISA). (2022

October 19). Avoiding Social Engineering and Phishing Attacks. CISA.gov.

Section: Phishing: "Smishing is phishing that uses text messages to trick a user... Vishing is phishing that uses a phone call to trick a user." This document clearly differentiates the terms based on the communication medium.