Can a single firewall cover multiple modules?
One of my players and I have been discussing the issue. Every time the book talks about firewalls it mentions them covering "modules" plural, but my player thinks this is an indefinite plural, and that if a single firewall could cover multiple modules, there would be no reason to include the following passage from page 217:
"A computer can have multiple firewalls to block off multiple modules, but no one module can be protected by more than a single firewall"
He thinks the first part of that sentence means that you need multiple firewalls to block off multiple modules, while I think it reads as saying that you "are allowed" to have multiple firewalls, each protecting different sections of the system.
Can anyone clarify this?
I believe your interpretation is correct. The reason not to do this is that once the firewall is overcome the hacker has access to all of the modules that the firewall protected rather than a single module.