Lsof is a Unix-specific diagnostic tool. Its name stands for LiSt Open Files, and it does just that. 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/11082/lsof_4.47_W.tar.gz
Source: https://packetstormsecurity.com/files/11082/lsof_4.47_W.tar.gz.html