You would like to block outgoing access to particular remote host/ip or port for all or selected service/port. In this quick tutorial I will explain how to use iptables to block outgoing access.
Block Access To Outgoing IP Address
The following rule will block ip address 202.54.1.22 from making any outgoing connection:
iptables -A OUTPUT -d 202.54.1.22 -j DROP
The above will block chat server ip address or site having dangerous contains such as viruses or malware.
Block Access To Outgoing IP TCP / UDP Port Number
To block specific port number such tcp port # 5050, enter:
iptables -A OUTPUT -p tcp --dport 5050 -j DROP
To block tcp port # 5050 for an IP address 192.168.1.2 only, enter:
iptables -A OUTPUT -p tcp -d 192.168.1.2 --dport 5050 -j DROP
Finally, you need to save your firewall rules. Under CentOS / RHEL / Fedora Linux, enter:
# /sbin/service iptables save
OR
# /etc/init.d/iptables save
For more information see iptables(8) or our Linux firewall tutorials from the following resources:
- CentOS / Redhat Iptables Firewall Configuration Tutorial
- Linux Configure Firewall Using Shorewall Under RHEL / CentOS
- Debian / Ubuntu Linux: Install and Configure Shoreline Firewall (Shorewall)
Linux Building Rules For The Cluster With Firewall Builder
Linux: 25 Iptables Netfilter Firewall Examples For New SysAdmins
40 Linux Server Hardening Security Tips [2019 edition]
30 Best Sources For Linux / *BSD / Unix Documentation On the Web
Top 25 Nginx Web Server Best Security Practices
Linux 25 PHP Security Best Practices For Sys Admins
30 Linux System Monitoring Tools Every SysAdmin Should Know
IPTABLES. I just want to know how to block a certain IP address or network to access a specific server. lets say the host/ip 192.168.1.2 will be block/denied access to server/ip 192.168.1.10
thanks
Not one freaking person on the whole internet has an example of how to use iptables to stop one single machine from being able to access one single IP address.
iptables -A INPUT -s 192.168.0.42 -d 202.54.1.22 -j DROP
Jes,
Drop single system 202.54.1.22:
Try following urls for more …
How do I Drop or block attackers IP with null routes?
Linux Iptables block incoming access to selected or specific ip address
HTH
Hi, Can anyone help?
How do I block the outgoing traffic from x IP address to y IP address, but allow the incoming traffic from y to x? For some reason when I accept input and then do output drop it doesn’t allow inputs. Additionally, I did:
/sbin/iptables -A INPUT -p icmp –icmp-type echo-reply -j ACCEPT
/sbin/iptables -A INPUT -p icmp –icmp-type echo-request -j ACCEPT
But can’t ping x from y and vice versa. Please help.
Thank you,
k.
This is old but whatever, for those who don’t know:
For dropping OUTPUT and accepting certain connections (by port or whatever):
You need to use either state module (or preferably nowadays, conntrack with ctstate) to allow ESTABLISHED,RELATED
And yes this applies to non tcp because:
ESTABLISHED
The packet is associated with a connection which has seen packets in both directions.
RELATED
The packet is starting a new connection, but is associated with an existing connection, such as an FTP data transfer, or an ICMP error.
–
For ping, you’ll need to allow OUTPUT icmp traffic if you’re setting the policy to DROP. That is: the proper icmp types. You’re better of rate limiting though (fragmented packets are generally nowadays an indication of malicious activity but that’s another story entirely).
You should also allow ESTABLISHED,RELATED for INPUT as well (think about what I pasted above, as to why that is: if you don’t then a connection-oriented protocol e.g., one that uses TCP, will have issues.. keep in mind it might not be that someone is connecting to your server but YOUR server initiates the connection = output and then the remote host responds but if you don’t allow related then you’ll run in to trouble. Keep in mind outgoing connection requests and how/what they do, ports included as well as what type of connection, when you’re thinking about this).
Your answer came a long time after but, hey, thanks! It gave me some enlightment.
Welcome! Hope it answered your question(s) (or if it wasn’t you – since different name – I hope that it was helpful or useful in any case).
Hi guys, Need help!!!!
Running red Hat Linux 7.1 2.96-98 and need to block a group of users using usernem from accessing internet. Limit the same users to have access between 1300 – 1400 hrs and 1600 – 1700 hrs. I’m using Linux as the proxy server. i’ve tried iptables -A OUTPUT -p TCP -m owner –uid-owner prince -j DROP, but this owner and –uid-owner are not recognised
Thank you
You need to get Latest version RHEL 5.x or CentOS 5.x. Your distro is outdated and no longer supported.
Good article, very useful for me
Tks a lot
JC
Thanks for the info dear .. Put some more info regd the bandwidth management
Hi Friends,
Iam using Fedora6.0 with squid server but clients accessing internet and mails in below iptable coniguration now i want to block internet for particular ip’s range (Ex: 192.168.1.10 to 192.168.1.50) and toplevel peoples wants full internet access (Ex: 192.168.1.51 to 192.168.1.55) please need some help
Note : Already blocked some sites for all (192.168.1.0/255.255.255.0) but 5 people wants full access how to configure my iptables pls helpme
****************PRESENT IPTABLE CONFIGURATION***********************
# Generated by iptables-save v1.3.5 on Tue Dec 29 11:20:21 2009
*nat
:PREROUTING ACCEPT [21:3311]
:POSTROUTING ACCEPT [1:241]
:OUTPUT ACCEPT [1:241]
-A POSTROUTING -o eth1 -j MASQUERADE
COMMIT
# Completed on Tue Dec 29 11:20:21 2009
# Generated by iptables-save v1.3.5 on Tue Dec 29 11:20:21 2009
*filter
:INPUT ACCEPT [3822:1594474]
:FORWARD ACCEPT [115:7616]
:OUTPUT ACCEPT [2702:1165159]
-A FORWARD -i eth1 -o eth0 -m state –state RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -i eth0 -o eth1 -j ACCEPT
COMMIT
# Completed on Tue Dec 29 11:20:21 2009
is it possible to blacklist (ban from all) a source IP that would it a specific port of your choice ?
a kind of trape…
hi, i am newbie in linux, I am using Fedora 6.0 with squid server
i want to block gmail to specific subnet , how can i do it ?
nice, concise, and exactly what I was looking for. Thanks
sir,
I am using Fedora 13 iptables i was blocking some websites. but selected user i have access perticuler websites.
plz find the some other commands.
sir,
I want to block a website from my linux server using iptables command for a local computer
How to block Gmail using iptables ? I am using CentOS 5.7.
There should be –dport not -dport otherwise you will get
iptables v1.3.5: multiple -d flags not allowed
Try `iptables -h’ or ‘iptables –help’ for more information.
the correct syntax is
iptables -A OUTPUT -p tcp –dport 5050 -j DROP
There should be ‘–dport’ not ‘-dport’ (double dash).
Dean Kamali, thank you very much. I spent a long time trying to figure out what was wrong until I saw your comment.
To clarify, dport has to have two dashes before it.
Hi,
Your Tuts are simply superb.
Please let me know the difference between using DROP and REJECT options .
Hi,
Can anyone suggest me for blocking the internet access through fedora DHCP only allowing intranet access.some user also access the internet through USB dongle while at the same time they connect to the intranet i want to block there internet access when they are in network..It is a small enterprise network currently running on windows 2008 server and using the fedora for DHCP and FTP services…pls help…..
hi guys, i want to allow one service which is published on live ip address with specific port like x.x.x.x:5768 through squid.
currently i am using RHEL 6.x and only specific sites are allowed through url_regix rule. so how can i implement this acl to allow only one web service on specific port.
Thanks
Hi All,
i want to block port 1202 & 22 for all the IP and only want to allow any specific Ip ex.1.2.3.4 in cent 5.9 64bit
Please help me to shortcut it.
Waiting for your reply.
Hi Mohsin,
Step 1 :
Step 2:
iptables save and restart
Your company network comprises of a number of publically accessible servers located in a DMZ and a number of hosts and a File Server located in the Internal Office Network. How you would configure the two Linux Firewalls (LF1 and LF2) using iptables program to allow the external world (INTERNET) access the services located in the DMZ, but on the other side to protect the Internal Office Network from INTERNET threats?
How you would configure the two Linux Firewalls (LF1 and LF2) using iptables program to allow the external world (INTERNET) access the services located in the DMZ, but on the other side to protect the Internal Office Network from INTERNET threats? The services located in the DMZ has mail server and HTTP server and on the office network there is a FTP server and 4 Computers. Thanks
Hi
I need to block the Internet access and LAN access to a computer with in the network using iptables.
Could you please help me on this..