What is the Alg.exe process in your Task Manager?
The alg.exe process is a valid Windows system process that runs in the background. The alg.exe file is a trusted Microsoft file. This process listens or sends data on open ports to the local network or over the Internet. The alg.exe process can also hide itself, log inputs, and monitor applications. ALG stands for Application Layer Gateway.
The Application Layer Gateway service is a component of the Windows operating system. Required if you use a third-party firewall or Internet Connection Sharing (ICS) to connect to the Internet. This program must not end in the Windows task manager or you will lose all internet connectivity until the next restart of your computer when the process starts again.
The alg.exe executable allows applications on a client computer to dynamically use passive TCP/UDP ports to communicate with known ports on the server machine to access applications residing on the machine regardless of the presence of a firewall application.
To solve the problem of the server initiating the connection to the client and the firewall going crazy, a different method was developed for FTP connections. This was known as passive mode, or PASV, after the command used by the client to tell the server that it is in passive mode.
In FTP passive mode, the client initiates both connections to the server, solving the problem of firewalls filtering the incoming data port connection to the client from the server. When opening an FTP connection, the client locally opens two random unprivileged ports (N > 1023 and N+1). The first port is used for communication, that is, it contacts the server on port 21 (the most popular port for FTP connections is 21), but instead of issuing a PORT command and allowing the server to connects to its data port again, the client will issue the PASV (passive) command. The result of this is that the server opens a random non-privileged port (P > 1023) on itself and sends the PORT P command to the client. Then the client initiates the connection from port N+1 to port P on the server for data transfer.
The alg.exe process uses port 1025 by default to listen. The absence of the alg.exe file would cause security protocols to block communication ports.
The conversion of address information for the network layer can also be handled by the alg.exe process, which extracts the application payload data residing within the acceptable address dictated by the host from either side of the host. NAT or firewall.
The function associated with the alg.exe process is similar to that of a proxy server that resides between the client’s communication line and the real server machine to facilitate data exchange.