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synos(1)		      Mail Avenger 0.8.4		      synos(1)

NAME
       synos - guess operating system from TCP SYN fingerprint

SYNOPSIS
       synos [--mtu mtu] [--db path] syn-fingerprint

DESCRIPTION
       synos takes a SYN fingerprint, in the format described for the
       CLIENT_SYNFP environment	variable in the	avenger(1) man page, and
       outputs a guess as to the type of the client operating system.  synos
       makes use of the	OpenBSD	SYN fingerprint	database (which	is also
       repackaged with Mail Avenger).

   OPTIONS
       --mtu val
	   Certain operating systems set the initial TCP window	size based on
	   the maximum transmission unit, or MTU, of the network.  For such
	   operating systems, synos usually checks the window size using both
	   the client's	MSS option plus	40 bytes (for TCP and IP headers), or
	   a hard-coded	MTU, which defaults to 1,500 bytes.  If	either value
	   works, the fingerprint is considered	to match the operating system.
	   You can change the value 1,500 by specifying	this option.  A	value
	   of 0	tells synos to use only	the value derived from the MSS option.

       --db file
	   Specifies an	alternate location for the SYN fingerprint database.

FILES
       /usr/local/share/pf.os
	   Default location of SYN fingerprint database.

SEE ALSO
       avenger(1), asmtpd(8)

       The Mail	Avenger	home page: <http://www.mailavenger.org/>.

       The OpenBSD home	page: <http://www.openbsd.org/>.

BUGS
       The operating system type is determined by heuristics that are not
       always reliable.	 Moreover, not all operating systems can be
       distinguished.  The database may	not even contain a client's particular
       operating system	and version.

       It is not hard to fool synos deliberately by changing TCP socket
       options or injecting raw	packets	onto the network.

AUTHOR
       David Mazieres

Mail Avenger 0.8.4		  2013-07-13			      synos(1)

NAME | SYNOPSIS | DESCRIPTION | FILES | SEE ALSO | BUGS | AUTHOR

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