On Wed, 17 Oct 2007 12:05:13 -0600, Ashley M. Kirchner wrote: > 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 Essentially, for any DROP rule, have a nearly identical LOG rule, with -j LOG --log-prefix "SOME STRING" instead of just -j DROP. For instance, I log the new not syn packets like so: -A INPUT -p tcp -m tcp ! --tcp-flags SYN,RST,ACK SYN -m state --state NEW -j LOG --log-prefix "NEW NOT SYN: " -A INPUT -p tcp -m tcp ! --tcp-flags SYN,RST,ACK SYN -m state --state NEW -j DROP Of course, the LOG rule must come before DROP. The rules are identical except for the jump part (-j).
