Question

A packet filtering firewall can

a)deny certain users from accessing a service

b)block worms and viruses from entering the network

c)disallow some files from being accessed through FTP

d)block some hosts from accessing the network

Answer 1

A packet filtering firewall will be able to look only till network layer because at that layer it is called packed. so it will be able to take decision on all the info it can see at that layer. at that layer ip of users are available . so it can discard packets according to ip. so answer d.  option a require a layer 4 firewall. (tl) option b requires layer 5 firewall (application layer) and option c may also need layer 5 .

Comments

why not (b) option please explain some more

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basically worms and virus are the piece of code that is written by a craker/hacker. so we can identify a worm or virus by seeing its code. so to see the code we need an application layer firewall as only application layer firewall are capable of seeing the data and can filter packets according to the code in it.