Problem 9.12 in \"Computer security principles and practice 3rd addition\" We ha
ID: 3694126 • Letter: P
Question
Problem 9.12 in "Computer security principles and practice 3rd addition"
We have an internal webserver, used only for testing purposes, at IP adress 5.6.7.8 on our internal coorporate network. The packet filter is situated at a checkpoint beetween our internal network and the rest of the internet. Can such a packet filter block all attempts by outside hosts to iniciate a direct tcp connection to this internal webserver? If yes design suitable packet filter rule sets that provides this functionality; if no, explain why a (stateless) packet filter cannot do it.
Explanation / Answer
Answer:
Yes a packet filter block all attempts by outside hosts to iniciate a direct tcp connection to this internal webserver and the set of rules for suitable packet that provides this functionality is given as below :
The outside hosts packet filter must not have any destination address that is in our internal webserver.
The incoming packet filter must not have a source address that is in our internal webserver.
The outside hosts packet filter must have a source address that is in our internal webserver.
The incoming packet filter must have a destination address that is in our internal webserver.
The packet filter that enters or leaves our internal webserver must have a source or destination
address that is within the scope of addresses in our internal webserver.
The packet filter rules can affect the transmission of packets and rules consists of User Datagram Protocol,Internet Control Message Protocol and TCP/IP protocol.
Normal firewall models check one section of the packet header i.e the destination and source address and they makes address constraints and rules designed to restrict packets with particular addresses from passing through the device system.
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