What is alg.exe?

Windows Process Description:
The process alg.exe or Application Layer Gateway Service is associated to the Microsoft Windows Operating System. The alg.exe process is a component of Internet Connection Sharing and Internet Connection Firewall. Upon its execution, alg.exe also calls a host of DLLs, Exes and other essential processes for the initialization of the Microsoft Windows Internet Connection and Internet Connection Firewall.

The alg.exe process is a valid Windows system process that runs in the background. The alg.exe file is a trusted file from Microsoft. This process listens to or sends data on open ports to the Local Network or via the Internet. The process alg.exe can also hide itself, record inputs and monitor applications.

The alg.exe file has a known file size of 44544 bytes and is located in directory C:\ Windows\ System32.

The alg.exe process or Application Layer Gateway (also known as Application Level Gateway) consists of security components that attaches implements a firewall to the computer network. The alg.exe also permits customization of the NAT traversal filters that are plugged into the gateway to support the address and port translation for a defined application layer “control/data” protocols. In order for these protocols to function through a NAT or a firewall, the application must know the address number combination that permits incoming packets, or the NAT to monitor the flow and open up port mappings dynamically as required. Valid application data can be transmitted thorugh the security checkpoints of firewall or NAT that should have blocked the traffic for not meeting the required filter criteria.

The alg.exe process can be compared to the functions of a proxy server that facilitates the transmission between the client and the real server.

Other functions that the alg.exe process offers are permitting client applications to use dynamic ephemeral TCP/ UDP ports, converting network layer addresses, recognition of application-specific commands and synchronizng between multiple streams of data between two exchanging hosts.

Microsoft Corporation

Author URL:

Part Of:
Application Layer Gateway Service

Memory Usage:
Low. The alg.exe uses 44544 bytes worth of RAM resources.

System Process:


Background Process:

Uses Network:

Uses Internet:

Hardware Related:

Common Path: