Most computer systems are (165) to two different groups of attacks: Insider attacks and outsider attacks. A system that is known to be (166) to an outsider attack by preventing (167) from outside can still be vulnerable to the insider attacks accomplished by abusive usage of (168) users. Detecting such abusive usage as well as attacks by outsides not only provides information on damage assessment, but also helps to prevent future attacks. These attacks are usually (169) by tools referred to as Intrusion Detection Systems.

（168）处是（）

A.power

B.rights

C.authorized

D.common

系统物理配置方案设计应该在（）。

A.系统开发之前

B.系统分析阶段

C.系统设计阶段

D.系统实施阶段