a. Why are stateful packet inspection firewalls inexpensive? b. In practice, are they fairly safe? c. Are SPI firewalls limited to SPI filtering? d. What firewall inspection mechanism do nearly all...

a. Why are stateful packet inspection firewalls inexpensive? b. In practice, are they fairly safe? c. Are SPI firewalls limited to SPI filtering? d. What firewall inspection mechanism do nearly all main border firewalls today use?

a. When NAT is used, why can sniffers not learn anything about the internal IP addresses of internal hosts? b. Why does NAT stop scan probes? c. Why is NAT traversal necessary? d. Is a NAT traversal method easy to select?