Which of the following refers to unsolicited advertising sent via email?

The term that refers to unsolicited advertising sent via email is SPAM. This type of email is typically sent in bulk to a large number of recipients, often without their consent. SPAM can include promotional material for various products or services, and it often clutters inboxes with irrelevant content.

In the context of cybersecurity and email management, SPAM is recognized as a major nuisance and can even pose security risks, as some SPAM emails may contain malicious links or attachments designed to compromise the recipient's system. Because SPAM is generally unwanted and can be disruptive, many email services incorporate filters to help users manage and reduce the amount of unsolicited mail they receive.

Other terms associated with email security, such as phishing and spear phishing, involve attempts to deceive users into providing personal information or accessing malicious links, but they do not specifically describe unsolicited advertising. Vishing refers to voice phishing, which is a similar scam but conducted over the phone. Therefore, SPAM is the correct answer, specifically describing unsolicited advertising sent via email.