How do I know if a remote machine is using Windows or Linux?

Question

Is there some way to run a command (such as ICMP message or another protocol), get a response from a remote machine (not on my own private local network) and analyze the message to find some evidence that this machine is running a Windows or a Linux operating system?

Answer 1

It isn't definitive but nmap will do this with the command nmap -O -v (see docs for more details) If you're running windows or want a gui, look at zenmap

Answer 2

If you're on an IPv4 network, just use ping. If the response has a TTL of 128, the target is probably running Windows. If the TTL is 64, the target is probably running some variant of Unix.

Answer 3

: Presumes ping service enabled on Windows local and remote hosts
:
del _IX.txt, Windows.txt
ping -n 1 [computername|ipaddress] | findstr /i /c:"Reply" > ttl.txt
for /f "tokens=1-9* delims=:=< " %%a in (ttl.txt) do (
    if %%i leq 130 (
       if %%i geq 100 (
          echo Windows & rem or echo %%c >> Windows.txt
       ) else (
          if %%i equ 64 (
             echo *IX & rem or echo %%c >> _IX.txt
          )
       )
    )
)

Answer 4

One way to go is to use NMap. From the response, it can guess the remote OS.

Answer 5

Package: xprobe 'OR' xprobe2
Description: Remote OS identification Xprobe2 allows you to determine what operating system is running on a remote host. It sends several packets to a host and analyses the returned answers. Xprobe2's functionality is comparable to the OS fingerprinting feature in nmap.

Example:
$ sudo apt-get install xprobe
$ sudo xprobe2 -T21-23,80,53,110 ###.###.###.###

Reference:
http://www.sys-security.com/html/projects/X.html
http://sourceforge.net/projects/xprobe/