Re: How would I do this? (expert tricks) OT

From: Marc Perkel
Date: Tue Jun 19 2007 - 15:36:16 EST



--- Jan Engelhardt <jengelh@xxxxxxxxxxxxxxx> wrote:

>
> On Jun 19 2007 10:14, Marc Perkel wrote:
> >>
> >> tcpdump -lni any port 25
> >> iptables -p tcp --dport 25 -j NFQUEUE
> >> ...
> >>
> >
> >Thanks Jan, but I'm not sure it answers my
> question.
>
> There's more than one way to do it.
>
> One is...
> tcpdump -lni eth0 tcp [extra operands to match SYN
> packets] |
> myprogram
>
> a longer one is to write your own netfilter
> userspace program
> that receives the TCP SYNs (by means of -j NFQUEUE)
> and does
> take action.
>
> Another one is to use -j LOG and let your program
> parse
> down /var/log/firewall. Like
>
> iptables -A INPUT -p tcp --dport 25 --syn -j LOG
> --log-prefix "[evil]"
> tail -f /var/log/firewall | grep '^\[evil\]' |
> myscript
>
> myscript:
> #!/usr/bin/perl
>
> while (defined(my $line = <>)) {
> my($ip) = ($line =~ /SRC=(\S+)/);
> # Do something
> }
>
> >I want to run a script every time a connection
> attempt is made in real time
>
> The scripts runs constantly, preferably.
>
> >with the IP address as a parameter to the script.
> How would I do that? Suppose
> >my script is:
> >
> >iplog <ipaddress>
> >
> >
> >
> >
> >
>
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Thanks Jan,

I think what you sent me is workable. I noticed it
goes to the file /var/log/messages. Is there a way to
make it go to a specific file? Thanks a lot for your
help. I've been experimenting with some new and very
interesting ways to catch spam and this could be yet
another breakthrough.






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