各位大大安安，今天写到一题关于登入接口如何设计比较安全的题目：
The following are three possible logon scenarios. Explain why option (c)
below is preferable in term of system security.
a.
Welcome to XYZ computing
Enter username: jones
Invalid username
Enter username:
b.
Welcome to XYZ computing
Enter username: smith
Enter password: password
Invalid access
Enter username:
c.
Enter username: smith
Enter password: password
Invalid access
Enter username: smith
Enter password: FpQr56
Welcome to XYZ computing
a的问题比较明显，我已经知道了。
我不太懂的是b和c的差别，
那句"Welcome to XYZ computing"的出现时机会对安全有什么影响呢？
感谢各位大大！