You need to identify potential security threats. Which of the following security breaches might occur under the current IT and security practices？（Choose all that apply）（）

A.A virus that infects an IT administrator’s client computer could gain domain administrator privileges

B.Couriers could gain access to domain administrator privileges

C.Business office staff could discover couriers’ passwords and use them to access couriers’ information

D.All users could use their user accounts to gain the ability to install untested security patches on their client computers