defense function

例句：

1. 1. The defense function of the city wallis to protect its citizens from invaders.
   城墙的防御功能是保护市民免受侵略者侵害。
2. 2. The defense function of acomputer program is to prevent unauthorizedaccess.
   计算机程序的防御功能是防止未经授权的访问。
3. 3. The defense function ofa firewall is to block unauthorized access to the network.
   防火墙的防御功能是阻止未经授权对网络的访问。