Security :: Debian 6: Iptables Blocking Certain IP Ranges On A Certain Port Range?
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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Mar 30, 2009
I am setting up a iptables firewall on one of our servers, and I would like to block a range of addresses from getting into the system. I am using a script that does a BLACKIN and BLACKOUT methodology for specific addresses. One example is the following:
Code:
$IPTABLES -A BLACKIN -s 202.109.114.147 -j DROP
...
$IPTABLES -A BLACKOUT -d 202.109.114.117 -j DROP
What would be the correct syntax to use if I wanted to block an entire remote subnet from getting into the server?
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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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Dec 31, 2010
I'm assuming that the following should block the complete 178.123.xxx.xxx address range.
Code:
iptables -I INPUT -s 178.123.0.0/24 -j DROP
Then I believe that I need to save this change.
Code:
service iptables save
iptables: Saving firewall rules to /etc/sysconfig/iptables:[ OK ]
However, I'm not so sure that it is actually working based on the fact that there continues to be access to my wiki from that address range. The following is after I made the firewall change.
Quote:
178.123.177.61 - - [31/Dec/2010:04:24:40 -0500] "GET /mywiki/Opera%20Web%20Browser?action=edit&editor=text HTTP/1.1" 200 6346 "-" "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1)"
code....
Let me state that I'm new at this iptables thing. I did some reading and decided that I need to make the above change to the firewall but it doesn't seem to make a difference.
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Aug 8, 2010
Is possible blocking web with content for adults with iptables?
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Feb 11, 2011
I set up iptables but it is blocking my SSH set up. I did allow it by opening port 22 but it did not work. Here is my config:
Code:
iptables -F
iptables -P OUTPUT ACCEPT
iptables -P INPUT DROP
iptables -P FORWARD DROP
### this should allow SSH traffic
iptables -A INPUT -p tcp --dport 22 -j ACCEPT
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
How do you allow SSH through the iptables firewall?
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Jun 6, 2011
I have a fiberoptic broadband 20MB synchronous pipe at my home. Over summer at my place of employment its pretty much dead for 3 months so when I'm not busy I play around on my home server. I have my 20mb pipe going directly into my wrt54gl, from there I have a wired connection going to my server (Centos 5.3 recently upgraded to 5.5 through updates.) It serves as a file server(Samba, SSH). My wrt54gl handles natting port 22 to my server. I have my wireless AP setup to hand out leases from .2-.20 and my server has a static of .100. Dyndns.org handles my name resolution via their free account method.
I have a Mac Pro, iMac, Macbook, and a Toshiba Laptop with 64bit 7 running off wireless along with our cell phones, and my XBOX 360 also is wired directly for the gaming speed. I use all of the computers around my home to access the samba shares via unc path for file sharing and or working on projects. I had originally planned to upgrade the wrt54gl with a cisco e3200 or an e3000 but unfortunately I've come to find out dyndns and the e lines of cisco wireless AP's dont work with dyndns and get banned. So I would have to install the daemon on my server and put it as a directly connected server to my WAN link and install a second ethernet card and pass traffic through my server for the rest of my home which I am not going to do.
All of the previous sentence because it would update dyndns with a 192.168.x.x address since its not directly connected. I use a combination of putty.exe and vnc viewer to tunnel 5900 through port 22 to my server. So from anywhere I am at I can access my screen securely and then rdp or vnc to the desktop of my local LAN computers. This allows me to only have port 22 open. I've been looking at my ssh logs and noticed I have been getting hit alot with ssh scans. I want to implement an iptables firewall on my linux machine just for the purpose of further securing port 22. I dont necessarily need natting on the iptables firewall but all I need is ssh in and out, web in, and samba out to local ip's only.
For SSH this is what I want. I want to allow SSH from any IP but if it tries to login more than 3 times in one minute I want to block that IP for a full minute before it can try 3 more attempts. I also would like log to a file but have been having issues getting that to work as well. That way when I review logs and I see that an ip tries three times and then waits a minute and tries three more, etc... I can permanently block that ip or range of ip's by adding it to the iptables script. Here is my current iptables script and it doesnt seem to be working for me. I have played with this and read for almost two weeks and still cannot get it to work correctly.
Code:
#!/bin/bash
# In order to use this iptables firewall script you must have iptables installed. You also must be using a 2.4.x series Kernel, with iptables suppport compiled into it, which is standard for most newer linux distributions.
# If you need help compiling iptables into your kernel, please see our kernel Compile/Upgrade Guide located at [URL]
# Once the script has been edited with all your relevant information (IP's Network Interfaces, etc..) simply make the script executable and run it as root.
# chmod 700 fw_rules.sh
# ./fw_rules.sh .....
# Our final trap. Everything on INPUT goes to the dropwall
# So we don't get silent drops.
$IPT -A INPUT -j dropwall
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Sep 3, 2011
How would one block an IP range access to a Debian-based Linux system for say 47.1.1.1. - 48.255.255.255? Would it be with the hosts.deny file? If so, how would it be written in the file? Also, would the system require being restarted for the changes to take effect, after writing to the file?
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Apr 15, 2011
I have the default to deny all. The only rule I have in there is:
Code:
To Action From
-- ------ ----
[code]....
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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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Feb 16, 2011
I have a mail server with IPTABLES enabled.I want to allow access to:
41.0.0.0/8
58.0.0.0/8
61.0.0.0/8
[code]....
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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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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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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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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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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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Jul 3, 2010
I'm trying to capture packets with WireShark on 2 port ranges.
This syntax is not working :
Quote:
bash-3.2# /usr/sbin/tcpdump -ttttvv udp portrange 8500-8600 and portrange 5060-5070
There is no output...
What is the correct syntax for defining multiple port ranges ??
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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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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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Nov 12, 2009
I want to block the icmp packets(ping) from the other computer to my RHEL-4 what's the syntax I should use to do so in IPTABLES.
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Aug 19, 2009
I want to block all the outgoing ssh form my machine, i.e my machine will not be able to ssh to any outside machine using iptables. The distro is RHEL, I added the following entry in the iptables but unfortunately it didnt worked, -A OUTPUT -p tcp -m tcp --dport 22 -j DROP
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Mar 17, 2010
i used the angry ip scan software and found alot of the public ip addresses on our network are accessable from outside when they are not suppose to, For eg printers/ pcs etc. to make a start on locking down the network i was wondering if anybody knew th iptables command to add a rule which blocked all incoming traffic to specific ip adresses on the network and to a range of ip addresses.
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Jul 9, 2011
Friends the following shall block a particular machine in the same network, what can be done if it is dynamic IP and from other network?
iptables -A INPUT -s 192.168.0.0/24 -m mac --mac-source 00:50:8D:FD:E6:32 -j DROP
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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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Jun 5, 2010
I have two asterisk servers each one behind a linux firewall/gw. Linux is Centos 5.4, kernel 2.6.18-164.el5, iptables v1.3.5. Routes on the fws are ok and when iptables is stoped the servers are see each other, all good. But when I run iptables script in any fw, one server (not always the same) goes unreachable. I verify this with asterisk -r, then show sip trunk, and status becomes UNREACHABLE.
Iptables scripts is generated by fwbuilder. The weird part is I put only one rule to de script and it looks like Source=any, Destination=any, Service=any, Interface=any, Direction (Inbound,Outbound)=any, Time=Any, Action=ACCEPT. So as you can see I tried something like "Do not do anything at all". But anyway I run the script in any fw and one server becomes UNREACHABLE. I think the script does something wrong after all or maybe I have some missconfiguration in my asterisk conf files. The point is I am not so expert in iptables or shell scripting so I can't see anything in the iptables script. I have look for some issues like iptables blocking because of ip_conntrack table full, or "dont fragment" bit set in kernel problem, but nothing seems to be the right problem at all.
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