[NTLUG:Discuss] iptable rules

[Terry Henderson]

Learning iptables...

Let's say there's a Trojan somewhere in a LAN.  Till it's found &
fixed, one might temporarily use one's firewall to limit access to
outside mail servers to a select few

Possible solution:  ???

First, block all access to outgoing port 25:
iptables -A OUTPUT -o eth2 -p tcp --dport 25 -j DROP

Second, allow users to send to select few:  [this is where I'm lost.]
iptables -A OUTPUT -o eth2 -to-destination 67.43.4.78:25 64.4.33.7:25
198.76.195 .112:25