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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Blocking incoming traffic with PF on OS X

The bigger picture is that I am trying to dynamically block/unblock IPs using fail2ban 0.8.14. I have been following an old guide for OS 10.5 with doesn’t include PF. I think I’ve configured ...
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2answers
13k views

UFW: Allow traffic only from a domain with dynamic IP address

I run a VPS which I would like to secure using UFW, allowing connections only to port 80. However, in order to be able to administer it remotely, I need to keep port 22 open and make it reachable from ...
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1answer
15 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
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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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2answers
32 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
16 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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1answer
1k views

Outgoing firewall application similar to Little Snitch for Mac

Is there a Linux application similar to Little Snitch? Little Snitch is an outgoing firewall that temporarily blocks outgoing network requests until the user decides whether to allow the connection or ...
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0answers
29 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
66 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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2answers
1k views

NAT and source IP filtering in PF, using OpenBSD >= 4.7

I just read a book about PF (The Book Of PF, No Starch), but there's one question not answered by it. If I have a gateway machine using two interfaces, $int_if and $ext_if, and I NAT the packages ...
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0answers
40 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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1answer
3k views

Installing pfSense firewall on an SSD

I was looking at creating a home firewall running pfSense (as I could not get IPCop to boot properly on my hardware). Doing a little research, however, I have some concerns with installing it onto an ...
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2answers
97 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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2answers
33 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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0answers
19 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
45 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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2answers
104 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 ...
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1answer
58 views

Blocking or forwarding packets as access point

I set up my Pi 2 as a wifi access point following this tutorial. I'd like to implement a rudimentary QoS, according to the DSCP field in every packet's header. That means, blocking packets using low ...
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1answer
167 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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1answer
29 views

ufw rule deny default outgoing

I want to deny all outgoing traffic by default, except ssh connections. I added this rules: ufw default deny outgoing ufw allow ssh Then I restarted the firewall by: ufw disable ufw enable ...
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1answer
66 views

Block outgoing connections to certain IP using PF

Can someone give me a hint on how to setup a basic deny rule whenever any TCP request is sent to a specific IP address? I am using the PF packet filter. Any help?
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1answer
182 views

How to combine iptables rulesets

Say there are several iptables scripts (run at boot time), all of which run something like iptables -A ... to add rules. I'm thinking this could be improved, turning all those shell scripts into text ...
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1answer
46 views

Block outgoing connection from running process

I have an java application that I have been developing. I use a external db server that I can't control. I want to simulate connection error to it, but I'm unable to do it. I have tried to use ...
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1answer
73 views

How to Mark Traffic using IPtables?

I'm trying to mark traffic, How shall I write following code in terms of IPtables? /ip firewall mangle> add chain=prerouting src-address=10.1.1.1/32 action=mark-connection \ ...
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1answer
507 views

iptables Port Forwarding — no service with the port

I have setup a network as in the image below: Firewall (FW) running CentOS 6 has two physical interfaces with subinterfaces: eth0:2 — 10.100.1.78/25 eth0:3 — 10.100.1.79/25 eth3 — 192.168.0.21/24 ...
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1answer
81 views

How to block telnet using iptables command

I am trying to block telnet on my server but I have failed to do so. I have added following firewall rules in INPUT chain of filter table for the same. INPUT CHAIN(filter table): <some other ...
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2answers
77 views

iptables configuration - ssh connection only from a remote network

I'm trying to configure Iptables of a server in order to permit SSH incoming connections only from a certain network. by the way this is the rule chain : # Drop anything we aren't explicitly ...
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1answer
11k views

Difference between SNAT and Masquerade

I am confused what's the actual difference between SNAT and Masquerade? If I want to share my internet connection on local network then whether should I select SNAT or Masquerade?
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Why is my laptop being blocked from connecting to a PPTP VPN server?

I have a fairly simple network at home Internet --> Modem --> Linux Router --> Switch --> Laptop The problem: There is a PPTP VPN server at work that I need to connect to from home. I configured my ...
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1answer
60 views

to allow certain ips and block all other connections on AMAZON EC2 ubuntu 12.04

How do I allow certain IPs and block all other connection in iptables on AMAZON EC2?
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1answer
132 views

is iptables broken on my raspberry-pi? how to fix?

I am getting some person(s) trying to brute force my ssh, from multiple ip addresses (small sample) : May 22 19:50:02 rpi sshd[1272]: pam_unix(sshd:auth): authentication failure; logname= uid=0 ...
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2answers
96 views

How can I allow SSH and SMTP only using IPTables?

I've got a raspberry pi set up to send me periodic emails. As it's connected to the internet 24/7, I need IPTables set up properly. I want to allow incoming SSH and allow emails to send out on port ...
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3answers
15k views

How can I block a range of IP addresses with an Amazon EC2 instance?

I know a certain range of IP addresses are causing problem with my server, 172.64.*.* what is the best way to block access to my Amazon EC2 instance? Is there a way to do this using security groups or ...
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2answers
14k views

IPTables - Port to another ip & port (from the inside)

I currently have a NAS box running under port 80. To access the NAS from the outside, I mapped the port 8080 to port 80 on the NAS as follow: iptables -t nat -A PREROUTING -p tcp --dport 8080 -j DNAT ...
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1answer
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Help about CentOS 7 apps & Driver [closed]

I'm using pc for several years but never tried Linux so I'm quite noob in this field. I'm using Autodesk maya, Nuke & will learn houdini very soon. I found that linux works faster for this apps so ...
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2answers
71 views

Determine what port OpenSUSE firewall is blocking

I am having a problem with the WebStorm IDE in that I cannot use its built-in FTP capabilities probably due to my OpenSUSE (Tumbleweed) firewall blocking some needed ports. I am assuming that because ...
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1answer
43 views

Linux IPTables - Ignore Range of IPAddresses

I am currently modifying some of my IPtables rules on a public server and have run into a bit of a dilemma. The goal is to do the following: Rate limit the amount of SSH connections that can be made ...
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equivalent of iptables rule in ip6tables

I m newbie in the iptables. I have the following iptables rules in the source code of a project iptables -t mangle -I PREROUTING ! -i br0 -p TCP --dport 45 -j MARK --set-mark 0x1000 iptables -t nat ...
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4answers
3k views

How to do domain filtering in Linux?

Preferably something similar to iptables. Basically, I want to do domain filtering/whitelisting/blacklisting like I would with IPs in iptables. Are there any recommendations on how to do this?
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firewalld isn't blocking/dropping ports for ports mapped from docker containers

I have firewalld installed and running on my machine. here are my active zones # firewall-cmd --list-all-zones ... drop (active) interfaces: enp2s0 sources: services: http https ssh ports: ...
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2answers
660 views

FreeBSD ipfw keepstate vs setup keep-state

A lot of examples where people are using keep-state with setup together. For example: ipfw add 1 allow tcp from any to me 22 setup keep-state Because of setup, this rule will allow only SYN ...
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3answers
68 views

How does the iptables work with IPv6?

I would like to set up a firewall on Linux Debian for IPv6. It is important to use iptables for me. I have tried to change the ipv4 folder to ipv6. How can I set up iptables for IPv6?
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1answer
35 views

package from IP arrives at certain port => open portrange to IP for x seconds

I have been toiling with an issue on iptables: I am trying to make a portrange open to a specific IP for x seconds/minutes as a result of a single packet being sent to a specific port. Not exactly ...
0
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1answer
643 views

How to configure Centos 7 firewallD to allow docker containers free access to the host's network ports?

I have docker installed on CentOS 7 and I am running firewallD. From inside my container, going to the host (default 172.17.42.1) With firewall on container# nc -v 172.17.42.1 4243 nc: connect to ...
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1answer
148 views

NFS Port Blocking Firewall Issue

I am a little stumped on this one and maybe I have been staring at this for too long...but I cannot get my Mac (10.10.3) machine to connect to my Oracle Linux 7 (CentOS/RH 7) server with its firewall ...
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1answer
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Is it better to set -j REJECT or -j DROP in iptables?

There's an example of iptables rules on archlinux wiki: # Generated by iptables-save v1.4.18 on Sun Mar 17 14:21:12 2013 *filter :INPUT DROP [0:0] :FORWARD DROP [0:0] :OUTPUT ACCEPT [0:0] :TCP - ...
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Disable networking only inside of a single terminal

I want to run a command in the terminal to disable networking, just in that terminal. How can that be accomplished? I'm running OSX. Note: I only want to disable the networking in that terminal. ...
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2answers
602 views

Is there any PF log parser for FreeBSD

I am runing FreeBSD 8 stable with PF as firewall, I am looking for any tool for parsing PF log's.
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103 views

How to create a rule on IPCop firewall for bittorrent trafic to work properly?

I've been trying to use my favourite torrent client (µTorrent) after setting up my IPCop (last update 2.1.9) and it warned me that my router/firewall was blocking the traffic and that I had to open a ...
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79 views

Redirect all ARP traffic from eth0 to eth1

I would like to redirect ARP traffic, but I'm struggling with arptables and ebtables. I have 2 interfaces: eth0 10.10.10.25 eth1 10.10.10.20 Both in 10.10.10.0/24 I want to redirect the ARP ...