Je nmap jasnovidec?

[9r na seznam.cz]

Petr Tomasek wrote:
> 
> Muzete me nekdo rict, jak to ta potfora (nmap) zjistil? Podle nejakych
> cisel packetu? Nemate o tom nekdo neco (text, atd)?
> 
> PT>
> -------------
> Starting nmap V. 2.54BETA24 ( www.insecure.org/nmap/ )
> Interesting ports on xxxxx (x.x.x.x):
> (The 1 port scanned but not shown below is in state: closed)
> Port       State       Service
> 80/tcp     open        http
> 
> Remote operating system guess: Linux kernel 2.2.13
> Uptime 31.528 days (since Thu May  3 01:37:04 2001)
> ^^^^^^^^^^^^^^^^^^
> Nmap run completed -- 1 IP address (1 host up) scanned in 2 seconds

nmap-2.54BETA24/docs/nmap_manpage.html:

      The  -O  option  also  enables several other tests.
      One is the "Uptime" measurement, which uses the TCP
      timestamp option (RFC 1323) to guess when a machine
      was last  rebooted.   This  is  only  reported  for
      machines which provide this information.

dle prislusneho rfc se do paketu dava nejaky timestamp, o kterem se pise

      The timestamp value to be sent in TSval is to be obtained from a
      (virtual) clock that we call the "timestamp clock".  Its values
      must be at least approximately proportional to real time, in order
      to measure actual RTT.

takze moznost, aby to nmap zjistil (a nebyl pritom jasnovidec),
existuje.

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