A firewall is a program that controls the incoming and outgoing network traffic on a system. Use this tag for all questions related to firewall configuration and operation.

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IPTables Firewall/Router/Gateway needing to block outbound traffic from users

I have multiple ethX interfaces. eth0 is connected to the internet. eth1 is connected to a trusted network. eth2 is connected to a network I need to impose usage rules. What I'd like to do is ...
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How to open server port on RHEL 6.6?

I am trying to open a port (tcp 27017) for access to mongodb on a newly created RHEL 6.6 instance at Amazon AWS. Following mongo docs, I did: sudo semanage port -a -t mongod_port_t -p tcp 27017 I ...
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OpenWRT on embedded device as firewall

I have the following setup in my network: My internet comes in through an ATT Uverse modem/router. The router is in bridge mode because that ATT Uverse modem/router connects to a second higher ...
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PPTP Through IPTables

If this has already been answered, I apologize, I could not find an answer to this during my searching. I am new at Linux/Unix and I have recently implemented a Raspberry Pi firewall/gateway on my ...
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1answer
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firewalld settings for OpenVPN with https, ssh, and smtp

I am configuring a remote CentOS 7 webapp server to wrap https and ssh inside OpenVPN, while keeping smtp running outside of OpenVPN. I notice that, when I establish an OpenVPN connection from a ...
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iptables v1.4.21: Couldn't load match `-d':No such file or directory [closed]

I am running kernel 3.14.18 and using iptables 1.4.21, built with these options: --static-enable --disable-shared When I run this command: /sbin/iptables -A PREROUTING -m -d 127.3.0.2/24 -j DNAT ...
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83 views

multiple user-types/access-rules for OpenVPN on CentOS 7 and firewalld

How can I define separate roles for users and administrator in OpenVPN running on CentOS 7 server? Specifically, the users must only be allowed to https, while the administrator must be allowed to ...
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How can I set up the ULOG target with iptables and MySQL

I'm running CentOS 6.6 32bit as a firewall box using iptables. I want to be able to use the ULOG target to store dropped packets in a MySQL database for statistical analysis. After much Googling I ...
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redirect all ARP traffic from eth0 to eth1

I would like tredirect ARP traffic. Im struggling with arptables and ebtables but i cant see the light :) I have 2 interfaces : eth0 10.10.10.25 eth1 10.10.10.20 Both in 10.10.10.0/24 I want to ...
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2answers
29 views

FTP and WWW services don't acknowledge connections

I have Lubuntu 14.04 LTS with vsftpd and the lamp stack (apache2, etc.) installed. Everything works fine on the LAN. Externally, the services don't acknowledge connection attempts. I can see packets ...
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42 views

Stateful user-space firewall for Linux

Is there any stateful user-space firewall for Linux? I'm looking for a firewall that doesn't rely on anything in Linux kernel (like iptables/netfilter) and works with raw packets.
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44 views

Open UDP Ports; Can I Close Them?

I'm trying to secure my internet browsing. I just reinstalled Xubuntu 14.04 and GUFW firewall. I have 8 UDP ports open. I don't understand why. The software I currently have open are Firefox, GUFW, ...
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16 views

What port uses my backportpackage or bzr?

I am working in a company what uses Ubuntu Precise on the desktops behind a proxy. The Proxy is available in /etc/environment and set as: http_proxy, https_proxy, ftp_proxy, no proxy and their ...
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1answer
78 views

How to use both syn proxy and connlimit rules with iptables?

I want to write both syn proxy and connlimit rules. I want to send packets to syn proxy first because of performance issue. Here is rule sample. I use bridge interfaces but I dont think it is ...
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kernel security and IDS Firewall + AV together or not?

I try to hardening my server. For doing so, I got a general question: Should I install kernel security patches like selinux and an Anti-Virus with Intrusion Detection Firewall? Does it make sense to ...
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0answers
73 views

How to setup reverse FTP in RHEL?

Researched: http://www.thecave.info/export-proxy-username-password-linux/ http://stackoverflow.com/questions/5334110/text-based-ftp-client-settings-behind-a-proxy ...
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1answer
45 views

Which port to open for Google HangOut Video Conference

We need to open the necessary ports for Google Hangout VIDEO Conferencing in our firewall. Unfortunately my netmon trace shows Port 51355 and 51336 to be active; which is not at all what the Google ...
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24 views

How to send all packets passing my firewall device to logging server?

I want to send all packets that pass my firewall device to logging server to inspect contents of passing packets on my logging server. It seems like my device doesn't support that feature explicitly ...
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1answer
266 views

Changed SSH port without allowing it through firewall, locked out now - what to do?

I have a VPS where I changed the SSH port from the default 22. Unfortunately I forgot to allow the new port through the firewall. I don't have physical access to the server, and my host does not seem ...
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36 views

firewall-cmd forward rules for interface with multiple ips

I'm looking for a way with firewall-cmd or another command to do the following. An incoming public interface has multiple ip addresses bound to it. How can I forward ports only for one of the ip ...
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iptables: using “conntrack” and “recent” modules to block unsolicited packets

When I only allow RELATED and ESTABLISHED packets, and DROP everything else, my firewall rules work perfectly and I have no problems: ### VARIANT A -A INPUT -i wlan0 -m conntrack --ctstate ...
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3answers
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what is dhcpv6-client service in firewalld, and can i safely remove it?

In a CentOS 7 server, I type in firewall-cmd --list-all, and it gives me the following: public (default, active) interfaces: enp3s0 sources: services: dhcpv6-client https ssh ports: ...
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1answer
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blocking all but specific ips from specific services in CentOS 7

In a CentOS 7 web server that needs to remain totally closed to the public, I need to block all ip addresses and then only allow specified ip addresses to access specified services. How can I ...
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97 views

Block all but specified range of ip's input to an specific port [duplicate]

In a CentOS 7 web server, how do I configure firewalld to block all but a specific list of ip addresses from making successful http or https requests? I know that I can use httpd.conf to restrict by ...
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how to make firewall changes permanent via firewall-cmd?

I am trying to open some ports in CentOS 7. I am able to open a port with the following command: firewall-cmd --direct --add-rule ipv4 filter IN_public_allow 0 -m tcp -p tcp --dport 7199 -j ACCEPT ...
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1answer
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libvirtd and filtered ports

I am new to virt-manager. After having configured a virtual network (new interface virbr0) with 2 VMs that should be able to communicate, I discovered that most ports are filtered. For example, the ...
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Linux Bridge Network with Static IP Addresses and Firewall

any and all help is appreciated. I am trying to set up my Network Map Can you give me advice in setting up my interface file? If I set a static IP on my PLC on the same gateway, I shouldn't need to ...
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38 views

iptables INPUT command

On a machine called ubuntu1, this is the iptables command: sudo iptables -A INPUT -p icmp -j DROP on the other computer (xp1) I can not ping the ubuntu1.So this is OK. But On ubuntu1 can ping xp1. ...
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Initial iptable rule and knockd operation in vps

Today I launched a vps with Debian 7 x64 and started playing around with it. I installed xampp as well as knock daemon to get my hands dirty. So, all I wanted to do was to actually block all requests ...
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2answers
39 views

iptables is ignoring rules?

I've found some strange traffic through tcpdump (traffic is ongoing always): 13:00:13.203754 IP 1.2.3.4.1028 > 188.113.188.16.56881: UDP, length 103 13:00:13.204396 IP 1.2.3.4.1028 > ...
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CentOS 7 Firewalld zone configuration for private web application

I have read all the man pages related to firewalld and also explored all of the files that come pre-installed in firewalld before it is configured. How can I configure the zones of the firewall to ...
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OpenVPN on Ubuntu VM

I am trying to create a VLAN Network from my home network for a web-dev platform. I am running Ubuntu servers in VirtualBox on a Windows 7 machine. I am running an Ubuntu DHCP/OpenVPN/Shorewall ...
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1answer
30 views

Iptable forward interfaces for gateway machine

I have two Ethernet interface being configured to use as system gateway ex: eth1: 10.10.1.0 eth2: 10.10.2.0 I want to forward all the packets which are coming to the 10.10.2.0 gateway contacting ...
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1answer
106 views

Assp won't start

I tried to install ASSP (Anti-Spam SMTP Proxy Server),but when I try to start it I get the following: $ perl assp.pl Perl version 5.012003 (5.12.3) is at least recommended to run ASSP 2.4.3 (14313) ...
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viewing firewalld logs via remote login to CentOS 7 server

I have firewalld installed in a remote CentOS server. When I log into the server over the internet as root, I type the following command to access the firewalld logs: journalctl ...
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281 views

Network firewall on CentOS, host cannot be resolved?

I have a centos machine and I am trying install some dependencies using yum. When I do this I keep getting a message saying the host cannot be resolved. I was told the previous person that used the ...
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1answer
43 views

Application specific DNS problem?

I'm working on a live stream transcoder application using nginx + ffmpeg. Everything works fine when I use avconv to transcode, but if I use ffmpeg, I get this error: [tcp @ 0xb4e9da0] Failed to ...
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1answer
73 views

Allow wifi connections only to a local service, don't route to the wired ethernet

I have a Raspberry Pi running Linux (Raspbian) which is connected to my corporate Internet over an Ethernet cable. The RPi also has a wifi adaptor plugged into a USB port. I've been following along ...
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1answer
468 views

log files in CentOS 7 [closed]

In CentOS 7, how can I locate and view all the system logs that tell me who tried to enter the system, who got in, what processes they contacted, what they accomplished, etc. I want to be able to ...
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2answers
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outgoing SMTP 25 port blocked by ISP?

I just setup postfix but I just realized my ISP outgoing blocks port 25 (SMTP). How do I send email outside? I can see my mail queue is filling up. Any suggestion?
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iptables: can't open tcp port

I'm running a Raspberry PI B+: Linux pi 3.12.28+ #709 PREEMPT Mon Sep 8 15:28:00 BST 2014 armv6l GNU/Linux The Raspberry is connect via lan (dhcp. ip: 192.168.78.29) to the local network. I'm trying ...
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47 views

Port randomly closing (iptables)

I'm running CentOS 6.5 on a VPS and one of the services I have running is murmur/mumble (A voip application). The issue I'm having is that the port clients connect on will be open when I initially ...
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1answer
22 views

Linux firewall techniques: MySql-Account

I'm having a discussion with a software developer in my nears. He is using MySql direct connections for a software. There is no PHP/SSH/whatever-Bridge involved for the communication, neither at ...
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1answer
92 views

Dovecot/Postfix mail server replies to [SYN] with [RST, ACK] when user attempts to connect (POP3). Likely iptables?

Currently I'm trying to troubleshoot an e-mail server that will allow users to send e-mail, but not log in to the server (POP3) or receive e-mail using their Outlook clients. Previously this was ...
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iptables fowarding rules

I have an iptables rule in the FORWARD section that looks like this: 17 0 0 CONFIRMED tcp -- * * 0.0.0.0/0 172.16.30.240 tcp spt:587 dpt:587 ctorigdst ...
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OpenVPN and routing problem on OpenWRT

My home topology: router1 (192.168.1.1) - D-Link dsl2540u server with static IP available from Internet (ADSL via ppoe). 4 LAN ports. router2 (192.168.1.2) - D-Link DIR-300 with OpenWRT. Plays ...
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92 views

Isolate subnets on the same interface

I need to isolate Subnets on a linux machine CentOS that act as gateway. I have the following scenario. CentOS eth0 pub ip addres eth0.1 192.168.1.1 eth0.2 192.168.2.1 Now eth0.1 and eth0.2 can ...
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59 views

Allowing web server communication in Linux firewall

I have a unique situation. Let's say my webserver ( e.g. 10.0.0.2) is connected to eth0 of my firewall (gw 10.0.0.1). A local network (192.168.0.0/24) is also connected to eth1 (192.168.0.1/24) of my ...
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79 views

How to set up a stateful firewall on an am335x Starter Kit board?

In the past, I have used the following script to set up a stateful firewall (on a normal x64 Ubuntu machine) without issue: iptables -P INPUT DROP iptables -P FORWARD DROP iptables -N TCP iptables -N ...
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Iptables and --tcp-flags

If I have the following rule in the nat-table in the prerouting chain: 0 0 REDIRECT tcp -- eth5 any anywhere anywhere tcp flags:FIN,SYN,RST,ACK/SYN redir ports ...