Nmap has a special flag to activate aggressive detection, namely -A. Aggressive mode enables OS detection (-O), version detection (-sV), script scanning (-sC), and traceroute (--traceroute). This mode sends a lot more probes, and it is more likely to be detected, but provides a lot of valuable host information. You can try aggressive detection with the following command:
# nmap -A <target> Nmap scan report for scanme.nmap.org (45.33.32.156) Host is up (0.071s latency). Other addresses for scanme.nmap.org (not scanned): 2600:3c01::f03c:91ff:fe18:bb2f Not shown: 994 closed ports PORT STATE SERVICE VERSION 22/tcp open ssh OpenSSH 6.6.1p1 Ubuntu 2ubuntu2.3 (Ubuntu Linux; protocol 2.0) | ssh-hostkey: | 1024 ...
