ISNprober is a tool that samples TCP Initial Sequence Numbers and can use that information to determine if a set of IP addresses belong to the same TCP/IP stack (machine) or not.
You can download it from the following link: https://packetstormsecurity.com/files/download/25260/isnprober-1.01.tgz
Source: https://packetstormsecurity.com/files/25260/isnprober-1.01.tgz.html

