Is it possible to detect the operating system type remotely from another system using any tools like nmap without admin privileges? What are the other alternatives for achieving this?

  • More details please? You can use nmap to scan the target os and it will make a good guess.... php scripts can also do it using $_SESSION[HTTP_USER_AGENT] but they would have to visit the page.
    – TheHidden
    Commented Mar 26, 2016 at 2:30
  • Here is a link that explains how nmap can perform OS detection and the appropriate command syntax. nmap.org/book/man-os-detection.html
    – user105637
    Commented Mar 26, 2016 at 4:27
  • You might find the p0f utility useful for this sort of thing.
    – Castaglia
    Commented Mar 29, 2016 at 6:50
  • No OS detection is performed when not using root user, no traceroute either. Yes you will be able to perform -A scan, but only with service discovery, just as you would with -sV flag.
    – Sab
    Commented Jun 26, 2019 at 1:15
  • Do you have a reference or a source that backs up the claim that "No OS detection is performed when not using root user"? This is the whole point of the question.
    – schroeder
    Commented Jun 26, 2019 at 6:48

3 Answers 3


Using nmap:

sudo nmap -O <target>

Or if they block your ping probes you can do:

sudo nmap -O <target> -Pn

Sometimes you still get fake results and you should try doing an aggressive scan (can be detected and blocked by the firewall).

sudo nmap -A <target>
  • 4
    OP asks explicitly for methods that work without admin privileges. I don't know why OP does, but this does not answer the question.
    – Tobi Nary
    Commented Mar 26, 2016 at 12:24
  • If I use "sudo nmap -O <target>" or "sudo nmap -A <target>" it prompts for password. My intention to find the OS type without using admin privileges and any passwords.
    – user45475
    Commented Apr 2, 2016 at 23:54
  • If I use "nmap -O <target> -Pn" it says replies as "TCP/IP fingerprinting (for os scan) requires root privileges.
    – user45475
    Commented Apr 2, 2016 at 23:56

You could use use the -T4 option together with the -A. No sudo is required (Tested on Ubuntu).

$ nmap -T4 -A

Would return for instance:

 Nmap scan report for
 Host is up (0.00060s latency).
 Not shown: 996 closed ports
 22/tcp open ssh OpenSSH 5.9p1 Debian 5ubuntu1 (protocol 2.0)
 | ssh-hostkey: 1024 00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:6c (DSA)
 |_2048 00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:6c (RSA)
 80/tcp open http nginx 1.1.19
 |_http-title: 403 Forbidden
 |_http-methods: No Allow or Public header in OPTIONS response (status code 405)
 111/tcp open rpcbind
 | rpcinfo:
 | program version port/proto service
 | 100000 2,3,4 111/tcp rpcbind
 | 100000 2,3,4 111/udp rpcbind
 | 100003 2,3,4 2049/tcp nfs
 | 100003 2,3,4 2049/udp nfs
 | 100005 1,2,3 46448/tcp mountd
 | 100005 1,2,3 52408/udp mountd
 | 100021 1,3,4 35394/udp nlockmgr
 | 100021 1,3,4 57150/tcp nlockmgr
 | 100024 1 49363/tcp status
 | 100024 1 51515/udp status
 | 100227 2,3 2049/tcp nfs_acl
 |_ 100227 2,3 2049/udp nfs_acl
 2049/tcp open nfs (nfs V2-4) 2-4 (rpc #100003)
 Service Info: OS: Linux; CPE: cpe:/o:linux:kernel

The -A tells nmap to perform OS checking and version checking. The -T4 is for the speed template, these templates are what tells nmap how quickly to perform the scan. The speed template ranges from 0 for slow and stealthy to 5 for fast and obvious.


You could use the nmap smb-os-discovery.nse script it should for the most part give you the right answers. It doesn't work on some versions of windows 10 though.

nmap --script smb-os-discovery.nse -p445

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