Context-based access control (CBAC) is a feature of firewall software, which intelligently

filters Filtration is a physical process that separates solid matter and fluid from a mixture. Filter, filtering, filters or filtration may also refer to: Science and technology Computing * Filter (higher-order function), in functional programming * Fil ...

TCP and UDP packets based on

application layer An application layer is an abstraction layer that specifies the shared communication protocols and interface methods used by hosts in a communications network. An ''application layer'' abstraction is specified in both the Internet Protocol Su ...

protocol session information. It can be used for intranets, extranets and internets. CBAC can be configured to permit specified TCP and UDP traffic through a firewall only when the connection is initiated from within the network needing protection. (In other words, CBAC can inspect traffic for sessions that originate from the external network.) However, while this example discusses inspecting traffic for sessions that originate from the external network, CBAC can inspect traffic for sessions that originate from either side of the firewall. This is the basic function of a stateful inspection firewall. Without CBAC, traffic filtering is limited to access list implementations that examine packets at the

network layer In the seven-layer OSI model of computer networking, the network layer is layer 3. The network layer is responsible for packet forwarding including routing through intermediate Router (computing), routers. Functions The network layer provides t ...

, or at most, the

transport layer In computer networking, the transport layer is a conceptual division of methods in the layered architecture of protocols in the network stack in the Internet protocol suite and the OSI model. The protocols of this layer provide end-to-end c ...

. However, CBAC examines not only network layer and

information but also examines the application-layer protocol information (such as

FTP The File Transfer Protocol (FTP) is a standard communication protocol used for the transfer of computer files from a server to a client on a computer network. FTP is built on a client–server model architecture using separate control and dat ...

connection information) to learn about the state of the TCP or UDP session. This allows support of protocols that involve multiple channels created as a result of negotiations in the FTP control channel. Most of the multimedia protocols as well as some other protocols (such as FTP, RPC, and SQL*Net) involve multiple control channels. CBAC inspects traffic that travels through the firewall to discover and manage state information for TCP and UDP sessions. This state information is used to create temporary openings in the firewall's access lists to allow return traffic and additional data connections for permissible sessions (sessions that originated from within the protected internal network). CBAC works through

deep packet inspection Deep packet inspection (DPI) is a type of data processing that inspects in detail the data (Network packet, packets) being sent over a computer network, and may take actions such as alerting, blocking, re-routing, or logging it accordingly. Deep ...

and hence Cisco calls it 'IOS firewall' in their Internetwork Operating System (IOS). CBAC also provides the following benefits: * Denial-of-service prevention and detection * Real-time alerts and audit trails

References

Computer access control Firewall software Packets (information technology) Data security Access control {{Compu-network-stub

See also

References