Ubuntu Security :: Iptables, Block Port Except For Eth0
May 24, 2011
I would like to allow incoming and outgoing connections when I'm connected to a wired connection, but drop it otherwise. I noticed that ufw can't block outgoing traffic because of will I give iptables a try. I'm unsure if dropping packages that are outgoing will work, the rule after the block rule will allow all outgoing connections.
This what the rules are intended to do, unsure if that is actually the case. Allow all loopback traffic. Allow ping replys Allow incoming on port 12345 if eth0, deny otherwise. Allow outgoing on port 12346 if eth0, deny otherwise.
Code:
iptables -A FORWARD -j DROP
iptables -A INPUT -i lo -j ACCEPT
iptables -A INPUT -p icmp --icmp-type 0 -s -m state --state ESTABLISHED,RELATED -j ACCEPT
[Code]....
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Jun 25, 2010
I have a Suse 10.3 router with 4 network cards. 1 is to connect to the big network and thereby also the internet, 2 are for 'client' subnets and I want to use the last one as a DMZ. In this DMZ will be a web server which has to be accessible from the other 2 subnets and from the big network. I could do it with a few simple clicks in Yast firewall, but I have some issues with this firewall and there for I want to use it as minimal as possible, using Iptables.
So now I'm struggling a bit with Iptables. Basicly what I'm looking for is how to block all ports but 80 in this last subnet with iptables.
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Apr 18, 2011
Is there any way to verify if packets being trafficked over a certain port are valid for the service you want to use this port for?
One obvious example that probably clarifies my question:
When I open port 443 (outgoing or incoming) for https/ssl traffic, I don't want this port to be used for say openvpn traffic.
Thus: when someone wants to surf to a website with https, it should be ok but if someone wants to connect to his home openvpn server over that same port, it should be blocked.
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Apr 20, 2011
I have a computer with two interfaces eth0(LAN) and eth1(WAN).I have followed some guides on the internet and came up with this iptables configuration:
# Generated by iptables-save v1.4.4 on Wed Apr 20 09:43:12 2011
*nat
:OUTPUT ACCEPT [0:0]
[code].....
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Mar 6, 2010
Is this how I would do that?
iptables -A INPUT -p tcp --destination-port 21 -d ! 168.192.1.2 -j DROP
This should block all incoming connections on port 21 from 192.168.1.2, correct? Thus preventing that IP from logging into my FTP.
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Mar 17, 2009
What i wanted to do was block everything from getting in my pc but still be able to surf the web and still use instant messenger.
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Jan 20, 2010
how to block all ports except pop,pop3,smtp in nat using iptables in squid on redhat A3
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Jun 8, 2011
My VPS host a mail, blog and web site. So i want to block port i not use. The port that i use is 80,21,2022,443. The other port will be drop. I want to block bad packet and all packet that not related. Can anyone how to write in iptables?
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Aug 11, 2009
I keep getting hundreds of SSH failed logins per day. Is there a way with iptables, i can say if a user connects too to port 22 over 8 times in 10 minuntes, then block them for an hour?
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Nov 18, 2010
I run SSH on a publicly open server and see following attempts in /var/log/auth.log which I was told by some one could be port scanning attempts.(Not sure though)
Code:
Nov 18 23:50:19 server sshd[21716]: Did not receive identification string from 186.0.80.197
Nov 19 00:05:57 server sshd[24056]: Did not receive identification string from 85.108.110.66
How can I block above such attempts?
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Feb 28, 2011
I've recently installed 10.10 server edition, and I must say it was a pleasant suprise, it's just the way I like it. I use it as a squeezebox-server. But I've run into a problem with the firewall. I did a portscan, which told me there are more ports open then I've told UFW to open. Among which port 25 and 119, when I telnet from another PC to those ports, the connection gets accepted, although there is no answer to any commands (as expected, there's no mail server running). Iptables print-outs also don't mention anything about the respective ports or a daemon that could be responsable, and the same applies to "ps -e" or "ps aux".
Iptables seems to be working, when I remove the rules to allow samba to work, I can't reach the shares, and when I insert them again I can reach the shares. "sudo ufw deny from any" as last rule doesn't change anything either (deny incoming is default (although I never issued the command "ufw status verbose" says it is) so it shouldn't, but ports 25 and 119 shouldn't be open either).
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Sep 5, 2010
I've got two virtual machines running, the first VM (VM1) has two network interfaces, one bridged with my real lan, one a private subnet. The second VM (VM2) has one nic, only on the private subnet.
I have VM1 acting as a router for VM2, giving access to my real lan for internet access. The problem I'm having is I cannot get VM1 to forward ports 80 (http) or 222 (ssh) to VM2 from my real lan.
Here is the script I've cobbled together from various (foreshadowing!) locations:
Code:
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Dec 24, 2010
I'm trying to open port 119. I already have a few ports open. I've used webmin to open both incoming and outgoing ports. iptables --list --numeric gives me:
Code:
...
ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:10000
[code]....
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Jan 9, 2010
I want to do port mapping on a linux machine using iptables.I have a service listeneing on port 2000 udp and I want to add iptables rule, which will map incoming packets on port 2001 to port 2000, so that service will accept the connections.The idea is that I don't want to change the default port for the service, but to make internal port redirection from (2001 to 2000), so the default service port will be filtered by iptables, and the other port will be open to the outside. The internet host connects to the linux machine on port 2001. The linux machine change destiation port from 2001 to 2000 and the service (on the same machine) process the packets and accepts the connection.I tried adding the following to my iptables rules, but it didn't work out:
$IPTABLES -A FORWARD -p udp --destination-port 2001 -j ACCEPT
$IPTABLES -t nat -A PREROUTING -i eth0 -p udp --dport 2001 -j REDIRECT --to-port 2000
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Nov 9, 2009
I'm using iptables with modules ip_contrack_ftp to be able to use passive ftp. It works well as long as port 21 is being used as listening port. Is there any way to make it work when I configure my ftp server (vsftpd) to listen on an alternative port, lets say 21001 or something? The helper module only seems to be working properly with the standard port, so I was wondering whether there was a way to "tell it" that another port is being used? I mean, of course I make a rule in fw to allow traffic to the alternative port.
But once it's time to start passive connection, then the iptable module cannot handle it properly. I could solve the problem by making a range of passive ports in the ftp-server configuration and allow the incoming traffic to them, but then using helper modules doesn't make any sense. I just want to allow the traffic to the listening port and then want the ip_contrack_ftp module to take care of the rest. This is what I do today - but only port 21 seems to be working. Is there a way to do this with a non-standard ftp port?
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Jan 3, 2011
how can i drop igmp port 0 packets with iptables rule? my log file is full of this router advertisement.
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May 16, 2011
I am currently running Debian 6. I would like to know if there is a way and how i would go about blocking a certain IP range from connecting to my server within a certain port range. Say for example.
i want to block ip range 123.123.123.* from connecting to my server on the ports 33000 - 43000. But, i want to allow them to connect on any other port range, and i want to be able to allow connections from my server to the blocked ip range on those same ports. so, blocking incoming only on the above port range.
using iptables.
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Jan 11, 2011
I am at a loss how to prevent Denial of Service attacks to port 25 and not block legitimate connections from 2 Barracuda 800(s) and block smart phones such as iPhones/Blackberrys/iPhones that use the server smtp.server.com for email.
Presently for port 25
RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 25 -j ACCEPT
The 2 Barracuda 800(s) make port 25 connections all the time, plus users with smart_phones have the incoming server type:
IMAP
pop.server.com
smtp.server.com
Is there a way to keep Denial of Service attacks from happening with iptables rules without causing blocking to the Barracuda(s) that make constant port 25 connections & smart phones that poll? I was thinking if I allowed the Barracuda(s) in these lines
-s (barracuda)24.xx.xx.xx -d (emailserver)24.00.xx.xx -p tcp -m tcp --dport 25 -m state --state NEW -j ACCEPT
Where the source would be the Barracuda going to the email server. It would be allowed, then I am left with how to allow other connections like Smart_Phones that connect via Port 25. I am thinking if I put rules in place doing connection counts in a minute it would result in errors connecting to the server and people would start complaining. Plus any limiting may result in blocking real traffic. Then would I need to allow the ISP range in the above example to accept port 25, I am still left with how to drop a flood/denial of service attack.
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Jul 13, 2010
I am setting up tomcat server on my Centos 5.5 machine. I've been advised to run tomcat on 8080 as non root user and redirect traffic to it from port 80.
I searched and found the following iptables commands for this:# iptables -t nat -A PREROUTING -p tcp --dport 80 -j REDIRECT -to-ports 8080
# iptables -I INPUT -p tcp --dport 8080 -j ACCEPTI have a doubt:
Tomcat is not accessible via port 80 without the second command. But the second command opens 8080 and makes it accessible over the internet (tomcat is accesible via both: www.<website>.com and http://<ip address>:8080). This doesn't seem right. Is there some simple (iptables) way to redirect traffic "internally" from port 80 to 8080 without having to open 8080 to the internet.
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Dec 23, 2010
I'm trying to limit access to port 8443 on our server to 2 specific IP addresses. For some reason, access is still being allowed even though I drop all packets that aren't from the named IP addresses. The default policy is ACCEPT on the INPUT chain and this is how we want to keep it for various reasons I wont get into here. Here's the output from iptables -vnL
[Code]...
Note the actual IP we are using is masked here with 123.123.123.123. Until I can get everything working properly, we're only allowing access from 1 IP instead of 2. We can add the other one once it all works right. I haven't worked with iptables very much. So I'm quite confused about why packets matching the DROP criteria are still being allowed.
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Jun 6, 2011
I'm trying to open port 8080 on my application server. I've included it in my iptables; however I still cannot access through ssh nor putty and it doesn't show up when I netstat either.Here is my iptables-config:
-A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
-A INPUT -i lo -j ACCEPT
-A INPUT -i eth0 -s xxx.xx.x.0/24 -j ACCEPT
[code].....
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Apr 4, 2011
I'm trying to use iptables in order to forward all the incoming packets for port 5555 to port 5556 on the same server (192.168.2.101).
I wrote the following commands:
iptables -A PREROUTING -t nat -i any -p tcp --dport 5555 -j DNAT --to 192.168.2.101:5556
iptables -A FORWARD -p tcp -m state --state NEW -d 192.168.2.101 --dport 5556 -j ACCEPT
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Feb 20, 2010
I'm using a Debian servers, as router/firwall.. I've two ethernet interfaces into the server, one for wan and one for lan. The i use SNAT so my LAN clients can access the internet throgh the debian router. That is working... Now i want to be able to access servers on the LAN site from the WAN site, and i wanna use port address translation (PAT). I have a FTP server running on a lan server, so i'm trying to portward port 21.
iptables -t nat -A PREROUTING -p tcp -i eth1 -d (WANIP) --dport 21 -j DNAT --to 192.168.1.2:21
When people try to access my FTP from the WAN site, they are redirected to the local FTP server, and they are promted for crendentials, but when the credentials are typed, and the local ftp server should answer the wan request, the connections dies.
The wan clients are being promted for credentials, so they are redirected to the local lan server, but after that the connections dies, so i think there is some kind of nat problem, when the local lan server is trying to respond to the wan request..
Here i my iptables script:
#flush table
iptables -F
#input regler
[code]....
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Aug 5, 2009
If I forward port 80 to port 3128 for squid with an iptable rule, does port 3128 have to be open on the firewall or is this all routed behind the firewall?
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Mar 25, 2010
I have a mail server on which I would like to block port 25 on my eth0 for everyone except our external spam filter. the problem is that I want our users to be able to connect via port 10025 which is forwarded to port 25, which then is blocked...
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May 10, 2010
I want to block all outgoing traffic with iptables and only allow a few specific websites. I would like to get the code to do so and also to revert the changes in case I want to unblock them.
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Aug 3, 2010
Currently I have 2 Lan card in My System one for communicate client pcs (Lan card Ip 192.168.1.100) and other for Internet (Lan card ip 192.168.0.100.) All client pcs are in 192.168.1.0 Subnet Here i implement my system as router through iptables all clients are communicate through only 192.168.1.100 (clients default gateway also 192.168.1.100) Now no problem for forward rules when my system is active all clients are get internet.
Output of iptables -L
Chain INPUT (policy ACCEPT)
target prot opt source destination
[code]....
Now i want to block some ip address and port ways i tried lot of things in internet when i type iptables -A INPUT -s 192.168.1.150 -j REJECT (i found in internet it will block that ip address for getting internet and any access through my sys)
Now th Output
Chain INPUT (policy ACCEPT)
target prot opt source destination
REJECT all -- 192.168.1.112 anywhere reject-with icmp-port-unreachable
[code]....
it will block icmp protocol only I want to know how block ipaddress and port address ways...
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Aug 5, 2010
Currently I have 2 Lan card in My System one for communicate client pcs (Lan card Ip 192.168.1.100) and other for Internet (Lan card ip 192.168.0.100.) All client pcs are in 192.168.1.0 Subnet
Here i implement my system as router through iptables all clients are communicate through only 192.168.1.100 (clients default gateway also 192.168.1.100) Now no problem for forward rules when my system is active all clients are get internet.
Now i have problem with blocking UDP protocols i tried lot of things in net iptables -A INPUT -s 192.168.1.0/255.255.255.0 -p UDP -j DROP
But it's not blocking UDP protocols (i change UDP to ICMP Protocols then icmp is blocked every ip address)
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Dec 24, 2008
in my office i have to block all messenger like yahoo messenger, windows live messenger, i have to block websites like www.yahoo.com, some more web sites. i need guidance through which i can accomplish this task through ip tables or through squid server. i can use squid but i had heard that squid blocks pop and smtp also. squid creates some problem in receiving and sending email. i am using red hat linux 4 box and installed squid having two ethernet card 1 is connected to adsl line and 2 is connected to switch. all clients will have proxy address of this linux box. guys need ur help ASAP.
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Apr 25, 2010
Just wondering if it is possible to block web access on a certain ip address with iptables.
Iv seen guides for blocking web traffic on a whole network but i want to just block a single host from accessing the web.
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