Phishing

What it means

CISA describes phishing as social engineering by email or malicious websites that solicits information by posing as a trustworthy organization. The UK NCSC adds the other goals: installing malware through links or attachments, and getting money transferred. Mass campaigns go to millions of inboxes; targeted ones are called spear phishing.

Phishers borrow trust in several ways: spoofing a real domain, registering a lookalike, faking a display name, or sending from a compromised account. Domain authentication with DMARC enforcement removes the first option for your domain, which is why the UK NCSC's anti-spoofing guidance ends with rejecting spoofed mail.

For legitimate senders the side effect matters too. Filters tuned against phishing are one reason unauthenticated or inconsistent mail lands in spam.