Which of the following is a common type of malware?

The identification of a Trojan horse as a common type of malware is accurate. A Trojan horse is a malicious program disguised as legitimate software that users are tricked into downloading and executing. Once installed, it can perform various harmful actions, such as stealing personal information, creating backdoors for other malware, or enabling unauthorized access to a system.

Antivirus software, while essential for detecting and defending against malware, is not a type of malware itself; rather, it acts as a protective measure against various malicious threats, including Trojans. A network router is a hardware device used to route data between different networks and does not fall under the category of malware. Similarly, a VPN client is a tool that allows users to create a secure connection over a less secure network, such as the internet, and is not associated with malware. Thus, the focus on the Trojan horse clearly highlights its role as a common and significant threat in the landscape of cybersecurity.