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Old 07-23-2007, 07:36 AM   #1
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Cool iptables security

Hello friends ,

This is my first Thread in the LQ Blog. I want to ask one question regarding iptables.
what is the difference in using a very strong iptables firewall (like arno or other complex iptables scripts ) and using simple script like this one.

Suppose m using a public ip

iptables -P INPUT DROP
iptables -P FORWARD DROP
iptables --flush # Flush all rules, but keep policies
iptables --delete-chain

iptables -P FORWARD DROP
iptables -P INPUT DROP
iptables -A INPUT -i lo --source --destination -j ACCEPT
iptables -A INPUT -m state --state "ESTABLISHED,RELATED" -j ACCEPT
iptables -A INPUT -p icmp --icmp-type destination-unreachable -j ACCEPT
iptables -A INPUT -p icmp --icmp-type time-exceeded -j ACCEPT
iptables -A INPUT -p icmp --icmp-type echo-request -j ACCEPT
iptables -A INPUT -p icmp --icmp-type echo-reply -j ACCEPT

iptables -A INPUT -p tcp --dport ssh -j ACCEPT
iptables -A INPUT -p tcp --dport http -j ACCEPT

iptables -A INPUT -j LOG -m limit --limit 40/minute
iptables -A INPUT -j DROP

as in this script i am not opening any ports (except 80 and 22 ) for the outsiders, so m i totally protected by this script or else i have to use complex iptables scripts to protect from the hackers.
Old 07-23-2007, 09:14 AM   #2
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There's no such thing as "totally protected". But this will not permit inbound connections except to ports 80 and 22, thus protecting any other services from attack. You may want to consider DROPing packets with state INVALID somewhere in there as well.
Old 07-24-2007, 11:52 AM   #3
Registered: Apr 2006
Location: Sweden
Distribution: CentOS, RHEL, SourceMage, OpenBSD
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There are also some other things you can do to prevent SYN floods and other kinds of attacks for example:
echo 1 >/proc/sys/net/ipv4/tcp_syncookies
echo 1 >/proc/sys/net/ipv4/conf/all/rp_filter
echo 1 >/proc/sys/net/ipv4/conf/all/log_martians
Also, you may want to consider filtering outgoing traffic too.



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