Logging denied packets (iptables)
Ashley M. Kirchner
ashley at pcraft.com
Wed Oct 17 18:05:13 UTC 2007
One of our offices has several network ranges blocked in iptables
(essentially '-A INPUT -s www.xxx.yyy.zzz/aa -j DROP'). What I'd like
to do is create a log entry each time a packet is dropped, IF it matches
any of those networks. I think I need to assign all of those networks
to a "group" and then log dropped packets from that group only. And
while I realize this might have other ramifications, such as logs
growing exponentially, for now we're taking small steps. Later on I can
then look for things like logging the same IP only once...
So how do I tell iptables to create a group or name, or whatever
it's called for those ranges, and then log dropped packets from those
ranges only? And to be quite honest, all I really care to see in the
log is something like '[standard log prefix] Packet DROP:
$source/$destination' (or $source-port/$destination-port) - I don't
really care for the lengthy log entry that iptables creates, such as
this example of an SSH-reject:
Oct 17 11:15:04 queenb kernel: SSH REJECT: IN=eth0 OUT=
MAC=00:30:48:33:96:22:00:07:50:49:df:7a:08:00 SRC=124.198.16.156
DST=207.174.xxx.yyy LEN=60 TOS=0x00 PREC=0x00 TTL=44 ID=38666 DF
PROTO=TCP SPT=48226 DPT=22 WINDOW=5840 RES=0x00 SYN URGP=0
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