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==Disable uptime detection from external mashines== With the right tools you can "sniff" the uptime of a linux mashine only by sending and analysing tcp packets. The tool nmap does such a test.
Example output from nmap: Interesting ports on 192.168.70.121: PORT STATE SERVICE 80/tcp open http 81/tcp closed hosts2-ns Device type: general purpose Running: Linux 2.4.X|2.5.X OS details: Linux Kernel 2.4.18 - 2.5.70 (X86) ''' Uptime 0.667 days (since Thu Oct 21 03:21:03 2004)'''
This uptime statistics can be disabled by running the following command:
echo 0>/proc/sys/net/ipv4/tcp_timestamp
running nmap after that:
... Running: Linux 2.4.X|2.5.X OS details: Linux Kernel 2.4.0 - 2.5.20 w/o tcp_timestamps ...
You can add that line above to you init script or modify /etc/sysctl.conf and add that line: net.ipv4.tcp_timestamp=0
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