Is a virus scanner necessary for each host even if a network has a firewall and malware scanning for emails?

A virus scanner is essential for each host because malware can bypass the defenses provided by firewalls and email scanning solutions. While firewalls are effective at controlling network traffic and preventing unauthorized access, they do not inspect files for malicious code that might be downloaded by a legitimate user or transferred through other means, such as USB drives or shared networks. Moreover, email scanning typically focuses on preventing malware from entering the network through email attachments, but it may not catch all threats, especially if they are encrypted or in a format that the scanner cannot analyze.

Having a virus scanner installed on each individual host provides an additional layer of defense that is crucial for detecting and mitigating threat vectors that can exploit vulnerabilities within the system itself. This local inspection helps in identifying and neutralizing malware that may have been missed by network-based defenses, ensuring that even if malware does slip through the firewall or email filters, it can still be caught and addressed on the endpoint before it can do harm. Overall, the combination of a firewall, email filtering, and dedicated virus scanning ensures a more robust security posture, capable of identifying threats at multiple levels.