Re: newbie question | prevent ICMP timestamp requests

From: David (thunderbolt01@netscape.net)
Date: 05/09/02 

From: David <thunderbolt01@netscape.net>
Date: Thu, 09 May 2002 15:19:26 GMT

evan.cooch@NOSPAMcornell.edu wrote:
> One of our IT folks here who is responsible for handling security on
> part of the network I work on ran a scan on all our systems, including
> my RH 7.1 box. He came up with several small little things for me to
> 'attend to'. One of them, however, is something I'm not quite sure
> what to do with. He mentions that my box is responding to ICMP
> timestamp requests.
>
> My limited understanding of such things is that this is one of the
> ways a DoS attack can be started - making lots of such requests.
>
> So, in an attempt to keep our IT folks happy - what is the easiest way
> to prevent ICMP timestamp requests? Please don't say 'configure
> ipchains' or 'install a firewall', unless these are the only options.
> I tried ipchains...once...and gave up trying to figure it out.
>
> Thanks!
>

If the system uses "sysctl" you can do it by adding this to
/etc/sysctl.conf and then restart the network.

# Turn off the tcp_timestamps
net.ipv4.tcp_timestamps = 0

If it doesn't use "sysctl" you can do it by adding this to the end of
/etc/rc.d/rc.local so it is run at system boot. Then also run it at the
command line if you want to activate it without a reboot.

echo 0 > /proc/sys/net/ipv4/tcp_timestamps 

-- 
   Confucius:  He who play in root, eventually kill tree.
Registered with the Linux Counter.  http://counter.li.org

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