“net1.exe” is known as the “Net Command for the 21st Century” (https://www.file.net/process/net1.exe.html). It is a PE binary file that is signed by Microsoft, which is located at “%windir%\system32\net1.exe”. On 64-bit versions of Windows there is also a 32-bit version of the file located at “%windir%\SysWOW64\net1.exe”.
Overall, the “net1.exe” was created as a temporary fix for the Y2K problem that affected “net.exe” (https://www.lifewire.com/net-command-2618094). There was an issue while using the command “net user [USERNAME] /times” which is responsible for configuring the logon hours of the user (https://web.archive.org/web/20140830150320/http://support.microsoft.com/kb/240195).
Thus, “net1.exe” is executed for specific functionality when “net.exe” is run (https://attack.mitre.org/software/S0039/). For example when calling “net time” an instance of “net1.exe” is started by “net.exe” using the command “net1 time” — as seen in the screenshot below.