Which of the following is NOT an example of malware?

Firewalls are security devices or software programs that monitor and control incoming and outgoing network traffic based on predetermined security rules. Their primary function is to protect systems from unauthorized access and cyber threats. They do not, in themselves, seek to cause harm or exploit systems, which distinguishes them clearly from malware.

In contrast, the other types of software mentioned—spyware, adware, and worms—are all considered forms of malware. Spyware collects information from a user's device without their knowledge, adware displays unwanted advertisements often leading to a negative user experience, and worms are self-replicating programs that spread across networks, often causing harm or consuming resources. Thus, the presence of firewalls as a protective measure highlights their role in cybersecurity rather than as a malicious entity.