1 The osf module does passive operating system fingerprinting. This modules
2 compares some data (Window Size, MSS, options and their order, TTL, DF,
3 and others) from packets with the SYN bit set.
5 [\fB!\fP] \fB\-\-genre\fP \fIstring\fP
6 Match an operating system genre by using a passive fingerprinting.
8 \fB\-\-ttl\fP \fIlevel\fP
9 Do additional TTL checks on the packet to determine the operating system.
10 \fIlevel\fP can be one of the following values:
12 0 - True IP address and fingerprint TTL comparison. This generally works for
15 1 - Check if the IP header's TTL is less than the fingerprint one. Works for
16 globally-routable addresses.
18 2 - Do not compare the TTL at all.
20 \fB\-\-log\fP \fIlevel\fP
21 Log determined genres into dmesg even if they do not match the desired one.
22 \fIlevel\fP can be one of the following values:
24 0 - Log all matched or unknown signatures
26 1 - Log only the first one
28 2 - Log all known matched signatures
30 You may find something like this in syslog:
32 Windows [2000:SP3:Windows XP Pro SP1, 2000 SP3]: 11.22.33.55:4024 ->
33 11.22.33.44:139 hops=3 Linux [2.5-2.6:] : 1.2.3.4:42624 -> 1.2.3.5:22 hops=4
35 OS fingerprints are loadable using the \fBnfnl_osf\fP program. To load
36 fingerprints from a file, use:
38 \fBnfnl_osf -f /usr/share/xtables/pf.os\fP
42 \fBnfnl_osf -f /usr/share/xtables/pf.os -d\fP
44 The fingerprint database can be downlaoded from
45 http://www.openbsd.org/cgi-bin/cvsweb/src/etc/pf.os .