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From: "Boris Karloff" <modelt20@canada.com>
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Subject: NMAP probing of network ports
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Hello:

How do I cause freeBSD 5.4 to not respond to an nmap
inquiry? I have already tried creating a line in rc.firewall
that says: 

${fwcmd} deny all from any to any
${fwcmd} drop all from any to any

I know these are active, since 1) I see them on the screen
at startup, and 2) pinging from any computer to any computer
results in a timeout.

(both of these should drop all TCP packets; but apparently,
they cause a RESET message to be sent.)

I've also tried adding the following to sysctl.conf:

net.inet.tcp.blackhole=2
net.inet.udp.blackhole=1

Again, these don't seem to prevent my freeBSD from sending a
packet (probably a RESET or UNREACHABLE-HOST ack).

Once the person sending the nmap to this machine has the IP,
its a simple step for them to ip-flood this machine; or
worse. 

How do I make freeBSD not acknowledge the fingerprint from
nmap?

Thanks in advance.

Harold.


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