Phishing is a form of social engineering and a scam where attackers deceive people into revealing sensitive information or installing malware such as viruses, worms, adware, or ransomware. Phishing attacks have become increasingly sophisticated and often transparently mirror the site being targeted, allowing the attacker to observe everything while the victim navigates the site, and transverses any additional security boundaries with the victim. As of 2020, it is the most common type of cybercrime, with the Federal Bureau of Investigation's Internet Crime Complaint Center reporting more incidents of phishing than any other type of cybercrime.

Modern phishing campaigns increasingly target multi-factor authentication (MFA) systems, not just passwords. Attackers use spoofed login pages and real-time relay tools to capture both credentials and one-time passcodes. In some cases, phishing kits are designed to bypass 2FA by immediately forwarding stolen credentials to the attacker's server, enabling instant access. A 2024 blog post by Microsoft Entra highlighted the rise of adversary-in-the-middle (AiTM) phishing attacks, which intercept session tokens and allow attackers to authenticate as the victim.

The term "phishing" was first recorded in 1995 in the cracking toolkit AOHell, but may have been used earlier in the hacker magazine 2600. It is a variation of fishing and refers to the use of lures to "fish" for sensitive information.

Measures to prevent or reduce the impact of phishing attacks include legislation, user education, public awareness, and technical security measures. The importance of phishing awareness has increased in both personal and professional settings, with phishing attacks among businesses rising from 72% in 2017 to 86% in 2020, already rising to 94% in 2023.

Phishing techniques and vectors include email spam, vishing (voice phishing), targeted phishing (spear phishing, whaling), smishing (SMS), quishing (QR code), cross-site scripting, and MiTM 2FA attacks.

Phishing attacks, often delivered via email spam, attempt to trick individuals into giving away sensitive information or login credentials. Most attacks are "bulk attacks" that are not targeted and are instead sent in bulk to a wide audience. The goal of the attacker can vary, with common targets including financial institutions, email and cloud productivity providers, and streaming services. The stolen information or access may be used to steal money, install malware, or spear phish others within the target organization. Compromised streaming service accounts may also be sold on darknet markets.

This type of social engineering attack can involve sending fraudulent emails or messages that appear to be from a trusted source, such as a bank or government agency. These messages typically redirect to a fake login page where users are prompted to enter their credentials.

Spear phishing is a targeted phishing attack that uses personalized messaging, especially e‑mails, to trick a specific individual or organization into believing they are legitimate. It often utilizes personal information about the target to increase the chances of success. These attacks often target executives or those in financial departments with access to sensitive financial data and services. Accountancy and audit firms are particularly vulnerable to spear phishing due to the value of the information their employees have access to.