Lsof is a Unix-specific diagnostic tool. It lists information about any files that are open by processes currently running on the system.
You can download it from the following link: https://packetstormsecurity.com/files/download/12755/lsof_4.37_W.tar.gz
Source: https://packetstormsecurity.com/files/12755/lsof_4.37_W.tar.gz.html