1, Web browsers and email clients are clearly _________ and they use _________ to provide their services.

2, Identify and briefly explain the four major security problems surrounding email.

3, Spams relies heavily on the absence of __________.

4, _________ email is the medium for distributing phishing attacks.

5, Early email viruses took advantage of the extensive capabilities of Microsoft's __________.

6,The first significant virus using Microsoft MAPI was named "Melissa" and appeared in early __________.

7, The ARPANET began as a(n) _________ network in 1969. 8, The ____________ system detects an intrusion and automatically implements security measures to block its operation.