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Layer 4 firewall is a device that can look at all protocol headers up to the transport layer and not the headers above that layer.

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2 Answers 2

No, it can't. There's no reliable way to identify the user at the Ethernet, IP or TCP levels, which is all it has to work with.

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You can firewall on a per-user basis only when firewall is running on the same OS instance the application the user is running.

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