Joel Reicher wrote:
Very simple script to insert a firewall rule for every matching IP:

# (run in a loop)
tcpdump -nlpi ppp0 port 123 and dst host 1.2.3.4 -c 100 > queue
for x in `grep "client, strat 0, poll 0, prec 0" queue | awk '{print $3}' | c
ut -d '.' -f 1-4`; do
grep $x banned &>/dev/null || (echo $x | tee -a banned; iptables -I INPUT -s $x -j NTP)
done


Maybe I'm missing something, but what's the point of doing this? Do we
know the virus stops polling, or changes its behaviour in any way when
faced with such a block?

Assuming it is a virus, since it seems real clients do this too :/

If a virus is using NTP, stopping it getting replies will let the clock drift so that it can't aim to start at the same time as other instances.


--
Simon Arlott

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