"osf" Passive OS fingerprint match

modulename: xt_osf.ko

Linux Kernel Configuration
└─> Networking support
└─> Networking options
└─> Network packet filtering framework (Netfilter)
└─> Core Netfilter Configuration
└─> "osf" Passive OS fingerprint match

In linux kernel since version 2.6.31 (release Date: 2009-09-09)  

This option selects the Passive OS Fingerprinting match module
that allows to passively match the remote operating system by
analyzing incoming TCP SYN packets.

Rules and loading software can be downloaded from

To compile it as a module, choose M here. If unsure, say N.

source code: