Commands using iptables (39)
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This appends (-A) a new rule to the INPUT chain, which specifies to drop all packets from a source (-s) IP address.
12iptables -A INPUT -s 222.35.138.25/32 -j DROP -
Stuck behind a restrictive firewall at work, but really jonesing to putty home to your linux box for some colossal cave? Goodness knows I was...but the firewall at work blocked all outbound connections except for ports 80 and 443. (Those were wide open for outbound connections.) So now I putty over port 443 and have my linux box redirect it to port 22 (the SSH port) before it routes it internally. So, my specific command would be:
iptables -t nat -A PREROUTING -p tcp --dport 443 -j REDIRECT --to-ports 22Note that I use -A to append this command to the end of the chain. You could replace that with -I to insert it at the beginning (or at a specific rulenum). My linux box is running slackware, with a kernel from circa 2001. Hopefully the mechanics of iptables haven't changed since then. The command is untested under any other distros or less outdated kernels. Of course, the command should be easy enough to adapt to whatever service on your linux box you're trying to reach by changing the numbers (and possibly changing tcp to udp, or whatever). Between putty and psftp, however, I'm good to go for hours of time-killing.10iptables -t nat -A PREROUTING -p tcp --dport [port of your choosing] -j REDIRECT --to-ports 22 -
5iptables -nL -v --line-numbers
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Safe for whitespaces in names.
5dpkg -L iptables | perl -lne 'print if -f && -x' -
Replace 10.0.0.0/8 with your largest local subnet. replace 10.1.1.123:3128 with your proxy information.. Note this only works with a proxy server configured for passive setup.. Now your firefox transparently proxy's stuff destined outside your network.. and Doesn't proxy stuff inside your network. as well as all your other favorite web applications. curl, wget, aria2 ect.
4iptables -t nat -A OUTPUT -d ! 10.0.0.0/8 -p tcp --dport 80 -j DNAT --to-destination 10.1.1.123:3128 -
Removes an iptables rule created by fail2ban. This example shows how to remove a rule for an IP from the fail2ban-SSH chain. Can be used for any service monitored by fail2ban. For more on fail2ban, see http://www.fail2ban.org/wiki/index.php/Main_Page
4iptables -D fail2ban-SSH -s <ip_address_to_be_set_free> -j DROP -
Retrieve top ip threats from http://isc.sans.org/sources.html and add them into iptables output chain.
4curl -s http://isc.sans.org/sources.html|grep "ipinfo.html"|awk -F"ip=" {'print $2'}|awk -F"\"" {'print $1'}|xargs -n1 sudo iptables -A OUTPUT -j DROP -d > 2&>1 -
4ASN=32934; for s in $(whois -H -h riswhois.ripe.net -- -F -K -i $ASN | grep -v "^$" | grep -v "^%" | awk '{ print $2 }' ); do echo " blocking $s"; sudo iptables -A INPUT -s $s -j REJECT &> /dev/null || sudo ip6tables -A INPUT -s $s -j REJECT; done
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2iptables -t nat -A POSTROUTING -p tcp --dport 25 -j SNAT --to-source IP_TO_ROUTE_THROUGH
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Then you can remove the specific entry: iptables -D INPUT 10 Just make sure these are set: IPTABLES_SAVE_ON_STOP="yes" IPTABLES_SAVE_ON_RESTART="yes" Else your changes won't stick when you restart iptables. Show Sample Output
2iptables -L INPUT --line-numbers -
For ipv6 use: grep -oE "\b([0-9A-Fa-f]{1,4}:){7}[0-9A-Fa-f]{1,4}\b"
2for idiots in "$(cat /var/log/auth.log|grep invalid| grep -oE '\b([0-9]{1,3}\.){3}[0-9]{1,3}\b')"; do iptables -A INPUT -s "$idiots" -j DROP; done -
This is just one method of checking to see if an IP is blocked via IP tables or CSF. Simple and to the point. Replace xx.xx.xx.xx with the IP you wish to check. Show Sample Output
1iptables -L -n --line-numbers | grep xx.xx.xx.xx -
show your current iptable rules from every available iptable table
1for i in `cat /proc/net/ip_tables_names`; do iptables -nL -v --line-numbers -t $i ; done -
1sudo iptables -L -nv
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Takes IP from web logs and pipes to iptables, use grep to white list IPs.. use if a particular file is getting requested by many different addresses. Sure, its already down pipe and you bandwidth may suffer but that isnt the concern. This one liner saved me from all the traffic hitting the server a second time, reconfigure your system so your system will work like blog-post-1.php or the similar so legitimate users can continue working while the botnet kills itself.
1tail -f /var/www/logs/domain.com.log | grep "POST /scripts/blog-post.php" | grep -v 192.168. | awk '{print $1}' | xargs -I{} iptables -I DDOS -s {} -j DROP -
Ddos syn attack
1echo 1 > /proc/sys/net/ipv4/tcp_syncookies echo 1 > /proc/sys/net/ipv4/ip_forward iptables -A FORWARD -p tcp ?syn -m limit -j ACCEPT -
Rather then editing the /etc/sysconfig/iptables file, or during a kickstart doing some awk/sed magic, easily add a rule in the correct place within iptables
1REJECT_RULE_NO=$(iptables -L RH-Firewall-1-INPUT --line-numbers | grep 'REJECT' | awk '{print $1}');/sbin/iptables -I RH-Firewall-1-INPUT $REJECT_RULE_NO -m state --state NEW -m tcp -p tcp --dport 80 -j ACCEPT -m comment --comment "Permit HTTP Service" -
1watch -n1 iptables -vnL
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1iptables -L -vnx --line-numbers; iptables -t nat -D <chain-name> <number>
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VPS server hosts suspect DOS attack if PPS is too high. This limits packets at the interface level. Do "sudo apt-get install iptables-persistent" to make persistent, or, if you already have, reconfigure with "sudo dpkg-reconfigure iptables-persistent" Show Sample Output
1sudo iptables -A INPUT -m limit --limit 2000/sec -j ACCEPT && sudo iptables -A INPUT -j DROP -
This turns your iptables packet filter to a "Allow any from any to any" filter, so you can rule out any filtering issues when you have a problem to enable a connection from or to your host. To re-enable it, run /etc/init.d/iptables restart
0iptables -F && iptables -X && iptables -P INPUT ACCEPT && iptables -OUTPUT ACCEPT -
I was previously unaware of the -v switch. As a result I never got specifics about which interfaces the allowed or dropped applied to. Thought I'd share the wealth... FYI, -n prevents DNS resolving of IPs.
0iptables -L -n -v -
Destination IPs will become invisible to source IPs!
0iptables -A FORWARD -i br0 -m iprange --src-range 192.168.0.x-192.168.0.y -m iprange --dst-range 192.168.0.w-192.168.0.z -j DROP -
a simple command in order to make iptables rules permanent, run @ sudo!
0iptables-save > firewall.conf; rm -f /etc/network/if-up.d/iptables; echo '#!/bin/sh' > /etc/network/if-up.d/iptables; echo "iptables-restore < firewall.conf" >> /etc/network/if-up.d/iptables; chmod +x /etc/network/if-up.d/iptables -
Clear iptables rules safely
0function clearIptables(){iptables -P INPUT ACCEPT; iptables -P FORWARD ACCEPT; iptables -P OUTPUT ACCEPT; iptables -F; iptables -X; iptables -L} - 1 2 >
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