中等ict-u08-d03
A firewall mainly:
A. Filters network traffic according to a set of rules✓ 答案
B. Compresses image files to save bandwidth
C. Replaces the need for antivirus signatures
D. Decides which video format a file should use
解說
A firewall applies rules about which connections are allowed, denied or logged, at the boundary of a network. It is one layer of protection and does not remove the need for patching, backups or user awareness.