Passive fingerprinting – Passive fingerprinting is the process of analysing packets from a host on a network. In this case, finger printer acts as a sniffer and doesn’t put any traffic on a network.

Common Os Detection Techniques are based on analysing:

IP TTL values; IP ID values; TCP Window size; TCP Options (generally, in TCP SYN and SYN+ACK packets); DHCP requests; ICMP requests; HTTP packets (generally, User-Agent field). MDNS ARP / NDP / SEND DNLA UPNP – SSDP M-SEARCH Bonjour / Zeroconf NetBIOS SSH / SSL / TLS SDP SNMP