How to block nmap's uptime detection?

[Alexander Demenshin]

On Thu, Jan 24, 2002 at 10:34:29PM -0500, Steve Snyder wrote:

> Running nmap against my firewall (from another network), it can 
> successfully report the uptime of my firewall machine.

  I am not sure but if you will drop packets to all unopened ports
  (instead of rejecting those), it might help.
  
  And, I found also that nmap's detection of uptime is unreliable,
  sometimes it reports wrong uptime (for Linux 2.4 at least).
  
  BTW, why do you want to hide this info? :)
  
/Al