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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how to safely increate ip_conntrack value

How do i calculate how much memory my single ip_conntrack connection will eat? I am planning to increate ip_conntrack on system but i want to be careful to not overcommit number. Is that any basic ...
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2answers
68 views

Is UFW behind a firewall(ed) gateway router necessary

Is it really necessary to run UFW behind my Gateway Router which already has Firewall/Port rules? In this example, I am discussing running UFW on an Internet Accessible (Linux) Server that is behind ...
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499 views

pfsense: squid transparent proxy not working in bridge mode

I have installed the latest version of pfsense. I have setup it up in bridge mode after creating a rule any for lan and wan respectively. I have setup the squid on transparent proxy mode with ssl ...
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1answer
115 views

ipset v4.5: Unknown set type

I compiled ipset on CentOS5 32bit machine and i am getting weird errors My kernel: [root@localhost ipset-4.5]# uname -a Linux localhost.localdomain 2.6.18-400.1.1.el5 #1 SMP Thu Dec 18 00:58:32 EST ...
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1answer
153 views

In what order are the rules handled in the Linux Firewall Module in webmin?

If I'm not mistaken it's top to bottom correct? And the catch-all default action at the end is to just drop any packets that don't match the rules above. Should I be logging the dropped packets as ...
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1answer
157 views

ufw allow ssh - and then connection gets lost

I'm trying to set up a debian server in the cloud, over SSH. I log in using a key. After the initial startup I want to set UFW: apt-get install ufw ufw allow ssh ufw enable This is how I've done ...
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1answer
30 views

Basic Hosting Postgresql in Virtualbox + Ubuntu 14.04

I have configured Postgres to accept network connections from anywhere: In pg_hga.conf: host all all 0.0.0.0/0 md5 In postgresql.conf: listen_addresses = '*...
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1answer
50 views

i have problem with firewall this question like this: [closed]

configure packet filtering firewall to allow DNS, HTTPS from outside to server configure PAT for HTTP using port 8080 from outside to server deny all other services and i have problem like this give ...
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1answer
1k views

Connection refused on port 8081 using curl

I have two CentOS 7 boxes, called Turbo and Demo. I started a daemon/service on the first one, Turbo, and wish to call the service from the second one, Demo. I started the service to monitor port 8081....
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1answer
86 views

Iptables: does dropping UDP packets take place in the user-space or kernel-space?

I know that Iptables is a user-space module, I also read it "configures" kernel modules to do big part of the filtering. So my question is, if I add a rule to allow only TCP:443 packets, would this be ...
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31 views

Debian 8 and few questions about Graphical Firewall?

So I have installed Debian 8 today and so far so good. What I want to achieve now is to install firewall but can't find Firestarter in repos (discontinued ?). So I have installed a GUFW and set it up ...
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17 views

Ubuntu Network Crashed?

So I have a server from ovh. When I was messing with the network I went to flush iptables and reload the network, and well it crashed all of the ports. So I thought I just need to reboot the server, ...
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37 views

How to customize Shorewall firewall logs

I am using Fedora 13 machine with shorewall installed. shorewall 4.6.6-RC1 iptables v1.4.7 Below is log format by shorewall: Oct 23 05:28:17 localhost kernel: shorewall:LAN-LAN:ACCEPT:IN= OUT=lo SRC=...
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50 views

How can I improve this script to install pptpd & csf on a Centos 6.5 openvz box?

I'm working on a script to ease the deployment of pptpd and csf on openvz boxes. Here's what I've got so far: echo "Installing epel repository, wget, and bind-utils..." yum -y install epel* yum -y ...
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1answer
40 views

iptables logging for all except ICMP

I have iptables firewalls and its logging for all DROP packets or Deny. I want to tell it to no LOG any packet for ICMP protocol. How do i tell that *filter :INPUT DROP [0:0] :FORWARD ACCEPT [0:0] :...
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1answer
26 views

firewall configuration to prevent a server-client malware connection

can i prevent a malware to connect on my pc simply setting ''incoming traffic to deny'' and allowing only outgoing traffic? I red that a malware could use the port knoking tecnique, but with a GUI ...
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52 views

How to Limit the hit-rate of connection for “X-Forwarded-for” IPs?

I have Apache, which is behind the Amazon ELB which forwards the IPs as in "X-Forwarded-for" header. I found some articles around to do the hitrate limitation but i doubt they are all for real IPs, ...
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Limiting number of simultaneous connections system-wide?

In my dormintory, I've got a not-so-nice networking environment, in which I'm identified only by mac-address of my ethernet card. In said environments, some limits of simultaneous opened connections ...
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80 views

UFW Preventing Web Browsing

I have the following rule set configured using UFW on Debian Jessie 8.2.0: Status: active Logging: on (low) Default: deny (incoming), deny (outgoing) New profiles: skip To ...
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2answers
165 views

Route incoming and outgoing on same interface

My router currently provides the NAT to all the PCs and the Ubuntu desktop (with some server functions) in the network. I want to use the Ubuntu system as a proper firewall, but it only has one ...
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1answer
41 views

How do I configure my server to stay hidden unless it receives correct password?

The server is supposed to silently ignore any requests (including ping) unless it receives correct credentials with initial request. Nobody else can tell that the host even exists. I am talking about ...
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1answer
569 views

Firewall blocking SSH/SFTP connections. How to cheat it?

Hi folks (sorry for the bad english) I'm a college student, and I live in the student's house of my university. I study computer science, and there we have the right to a space in a nfs server to ...
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27 views

how to set the ip tables for two vpns connected togheter

Immagine this scenario: two vpn. The first vpn is on the host sistem and the second is on a virtual machine. I want to connect to the first vpn and then to the second vpn on the VM, so i set ...
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30 views

Forward public network around current network

For the purposes of this discussion, I have a very current always-on linux machine with two nics: wifi0 eth0 A very crude diagram of my desired configuration looks like this: ...
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1answer
88 views

how to set ufw firewall/iptable rules for a VPN Server to be explicit in allowing certain connections?

I want to connect to a VPN. I want to enable ufw firewall or iptables so that there is no connection that goes out of the VPN tunnel or that comes in (except that for VPN server). Could you ...
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2answers
46 views

Domain only for web server

I have a domain which I want to point to my server. But I don't want to allow other people to use this domain to reach the server, only specific ports on the server (web server, so port 80). So if ...
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2answers
109 views

Best practises: Applying iptables firewall rules for SSH

I need to add some firewall rules in our QA environment using iptables. I have to do the changes remotely . Some of the changes also include disabling SSH for few Networks . What are best practices ...
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1answer
428 views

Why does iptables accept packets on a given port, when it is closed?

Here is my situation. I have a public address on my router and have manually forwarded a given port for torrenting, so not via UPnP, that is disabled both in the router and the application. It works ...
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1answer
226 views

How to set up a clear SuSE-Firewall?

I’m doing some rules in a machine with the firewall disabled, but when I run rcSuSEfirewall2 a lot of rules and policies are applyed by default: iptables -L Chain INPUT (policy DROP) target prot ...
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1answer
347 views

ufw won't allow connections to port 5432

I've installed Postgresql 9.4 on Ubuntu Trusty from the PGDG ppa. I've created a database and set it listen-addresses to '*'. I've made an entry in the pg_hba.conf file. I can connect locally with no ...
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23 views

Separation between the User machine and Server machine by another linux for monitoring

I am planning to have three virtual machines with virtual box (m1, m2,m3). I already installed on m1 = Windows XP Home Edition, and on m2 = LUbuntu 15. The big picture is this : m1 : a user m2 : ...
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51 views

Firewall Rule Testing - telnet failing

I am testing firewall rules but the telnet is failing. The firewallrules have been implemented but the target server is not listening on the servers. How can I enable the target server ports to ...
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1answer
356 views

iptables - how to drop protocols [closed]

I have the desktop-server Debian Jessie machine running for testing purposes just for 19 hours now. I have already set a few rules as you can see above. But I am not really into networking. So it ...
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183 views

iptables: block communication with others in same subnet

I have a couple of devices in my subnet (e.g. 192.168.0.0/24) and would like to make sure that one of these devices (identified by MAC or IP) can only talk via the router (where I'd like to set up ...
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166 views

Wireless ssh “issue” (No route to host)

I installed Debian Jessie (gnome) on one of my machines today and it went smoothly except for the wifi. Calling this machine A, I set up an ssh connection with machine B (using an rsa key) and then I ...
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1answer
749 views

iptables - why do I get “Table does not exist (do you need to insmod?)”

I need to install some iptable ruels to block traffic that originates from a certain country, I found this script example on http://www.cyberciti.biz/faq/block-entier-country-using-iptables/ it works ...
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1answer
89 views

Iptables rule to drop packets to and from local network

I want to set a virtual machine on laptop, but I don't trust the guest system fully, so I would like to block it's access to local network (to network 192.168.0.1/16 or 10.0.0.1/8 or ... the other one ...
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2answers
231 views

Using IPTables to Block Ports to Class A Subnets While Allowing Web Ports (80/443)

This is about a cPanel server which, like most servers, is under constant attack from lands afar. Considering that I only host to clients in the US and Canada, there is less of a reason to allow full ...
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3answers
217 views

How to stop outbound ftp from being established. centos/ rhel

What is the method to block a machine from establishing connection to an outside ftp server. Both ftp and sftp. inet, iptables, shutdown service?
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85 views

Unlocking all ports in a router when using Linux

I heard that Linux's open ports are not very vulnerable, so a normal desktop Linux installation doesn't need a firewall. Still, my router (Dlink) blocks some ports, even in LAN. Would it be a bad ...
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1answer
99 views

Advanced Policy Firewall: allow_hosts.rules doesn't work

I'm trying to open ports for Nimsoft. In allow_hosts.rules I opened ports for private network: tcp:in:d=48000_48020:s=10.0.0.0/8 tcp:out:d=48000_48020:d=10.0.0.0/8 During starting apf I see that ...
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56 views

Linux VM as a firewall

I have 3 vms a->b->c. I want to setup b as a firewall. Traffic is routed from a to c through b and I put a file on c. How do I show that b works as a firewall (first show that you are able to transfer ...
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3answers
622 views

Port is open but I can't ssh to it

My company PC is behind the firewall, I want to connect to my remote server. The port is open however I can not connect to it, does anyone know the root cause? From my company PC connect to my ...
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336 views

Change timeout of an entry of ipset with iptables rule

I'm trying to create a set with ipset and using it in some iptables rules. ipset has timeout option to set a countdown timeout to an entry of a set to automatically remove it after a period of time. ...
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2answers
4k views

How to let the Firewall of RHEL7 the SNMP connection passing?

How to let the Firewall of RHEL7 the SNMP connection passing? When I did this command on the computer: systemctl stop firewalld All the SNMP packet are passing well. When I restarted firewalld ...
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104 views

Working with firewall-protected server through ssh (dynamic IP)

I need to work on a Debian 6 server through SSH. The server is firewall-protected and SSH connections are filtered based on the user IP. Unfortunately I have an ISP provider with dynamic IP - it's ...
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42 views

Is there any way to configure fully automated proxyclient for workstations?

My network diagram is similar to above image; pc-router is also acting as firewall & I'm running squid on it. pc-router is running debian Vlan having workstations running fedora, ubuntu and ...
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1answer
142 views

iptables to block all websites

I have Debian 7, and I want to block all websites in my computer, unless my email, using IPTABLES or others firewall. How can I block all website, include http and https too. How can I do this?
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1answer
753 views

Which ports should I open for apt-get to work?

I installed Webmin, and then set up the firewall like this: INPUT SSH port ALLOWED Webmin port ALLOWED HTTP port (80) ALLOWED DROP EVERYTHING ELSE FORWARDING no rules OUTPUT no rules If I remove ...
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2answers
3k views

Error when redirecting ports with iptables: No chain/target/match by that name

I am trying to redirect all incoming TCP connections, originally to port 80, to port 8090, because I am running Confluence in 8090 and I want to avoid it running as root, which is a requirement to ...