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Blocking Incoming Traffic


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You want to block all incoming network traffic, except from your system itself. Does not affect outgoing traffic.

 

 

 

For iptables:

 

# iptables -F INPUT

# iptables -A INPUT -m state --state ESTABLISHED -j ACCEPT

# iptables -A INPUT -j REJECT

 

 

For ipchains:

 

# ipchains -F input

# ipchains -A input -i lo -j ACCEPT

# ipchains -A input -p tcp --syn -j REJECT

# ipchains -A input -p udp --dport 0:1023 -j REJECT :P

 

 

johnny06

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  • 1 month later...

slight refinement..

 

# iptables -F INPUT
# iptables -A input -i lo -s 127.0.0.1/8 -d 127.0.0.1/8 -j ACCEPT
# iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
# iptables -A INPUT -j DROP

 

ensures that loopback is actually looping.. addition of RELATED state (for instance passive ftp, dcc connections) and DROP rather than REJECT. Drop throws them away, Reject responds.. always better to be non-existant instead of visible..

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