Which of the following is a common type of phishing attack?

Answer: Spear phishing

Explanation: Spear phishing is a targeted phishing attack that focuses on specific individuals or organizations, using personalized information to appear credible and trick the target into revealing sensitive information or taking harmful actions.

Context: The other choices are different types of attacks — denial-of-service disrupts availability, malware injection involves introducing malicious code (which can be delivered by various methods), and SQL injection exploits database vulnerabilities. These are not categories of phishing.