{{Short description|Type of firewall in computing}}
A '''circuit-level gateway''' is a type of [[Firewall (networking)|firewall]].
Circuit-level gateways work at the [[session layer]] of the [[OSI model]], or as a "shim-layer" between the [[application layer]] and the [[transport layer]] of the [[TCP/IP]] stack. They monitor TCP handshaking between packets to determine whether a requested session is legitimate. Information passed to a remote computer through a circuit-level gateway appears to have originated from the gateway. ThisFirewall traffic is usefulcleaned forbased hidingon informationparticular aboutsession protectedrules networksand may be controlled to acknowledged computers only. Circuit-level firewalls conceal the details of the protected network from the external traffic, which is helpful for interdicting access to impostors. Circuit-level gateways are relatively inexpensive and have the advantage of hiding information about the private network they protect. On the other handHowever, they do not filter individual packets.
