Which of the following is a common method used in DoS attacks?

Traffic flooding is a common method used in Denial of Service (DoS) attacks because it involves overwhelming a target server or network with an excessive amount of traffic. The goal of this method is to consume all available resources of the target, such as bandwidth, processing power, or memory, thereby making the service unavailable to legitimate users. In this context, the attacker's system sends a surge of requests or data packets to the targeted server, often rendering it unable to handle normal traffic.

Other methods listed, such as phishing emails, malware installation, and password cracking, serve different purposes in the context of cybersecurity. Phishing is primarily about tricking users into revealing sensitive information, while malware installation typically refers to installing harmful software on a victim's device. Password cracking focuses on gaining unauthorized access by breaking or guessing passwords. These activities can contribute to security breaches but do not specifically embody the concept of denying service to legitimate users, which is the hallmark of DoS attacks.