a group of computers that are controlled by software containing harmful programs, without their users' knowledge

Botnets have evolved quickly to make detection more difficult. 僵尸网络发展迅速，使检测变得更加困难。

The hacker gained unauthorized access to the Penn computer server by using a botnet. 黑客通过使用僵尸网络获得了对宾夕法尼亚大学计算机服务器的未经授权的访问权。