stateful packet inspection -- relation to clients' computer security

What does the "state" of a TCP/IP packet have to do with whether it is from a user-requested web site, or from a hacker trying to gain access to a client computer, with reagrd to the "stateful packet inspection" that presumably only hardware firewalls are capable of?
Casey ClaassenAsked:
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rsivanandanCommented:
To simply look at it,

If the packet coming from outside

1. Has SYN and ACK bit set then it means that the connection was indeed originated from the inside machine and that is why acknowledgment is coming.

2. After that every packet passed has sequence numbers which are math bound and has relation with the packet sent.

So keeping the state information helps find it.

Now if a hacker sends a reply packet with 'syn' and 'ack' bit set, the machine won't entertain it since it didn't originate that traffic at all.

Does that help?

Cheers,
Rajesh
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Casey ClaassenAuthor Commented:
Yes, that does indeed help!
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