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