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Questions tagged [firewall]

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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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As I understand this, firewalls (assuming default settings) deny all incoming traffic that has no prior corresponding outgoing traffic. Based on Reversing an ssh connection and SSH Tunneling Made ...
Ali's user avatar
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73 votes
6 answers
309k views

How do we allow certain set of Private IPs to enter through SSH login(RSA key pair) into Linux Server?
Ranjan Kumar's user avatar
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69 votes
3 answers
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I am confused what's the actual difference between SNAT and Masquerade? If I want to share my internet connection on local network, should I select SNAT or Masquerade?
Chankey Pathak's user avatar
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59 votes
9 answers
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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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54 votes
2 answers
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I'm trying to connect to port 25 with netcat from one virtual machine to another, but it's telling me no route to host, although I can ping.  I do have my firewall default policy set to drop, but I ...
Katz's user avatar
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51 votes
5 answers
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I have a system that came with a firewall already in place. The firewall consists of over 1000 iptables rules. One of these rule is dropping packets I don't want dropped. (I know this because I did ...
Shawn J. Goff's user avatar
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50 votes
7 answers
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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 ...
adapt-dev's user avatar
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46 votes
9 answers
284k views

I want to set up CentOS 7 firewall such that, all the incoming requests will be blocked except from the originating IP addresses that I whitelist. And for the Whitelist IP addresses all the ports ...
Krishnandu Sarkar's user avatar
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44 votes
1 answer
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Do you need to run any of these commands: sudo ufw reload sudo ufw disable sudo ufw enable after adding a rule via sudo ufw allow?
iLW's user avatar
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41 votes
4 answers
229k views

How do I allow certain ips and block all other connection in iptables?
David's user avatar
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39 votes
1 answer
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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 - [0:0]...
Mikhail Morfikov's user avatar
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37 votes
2 answers
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I know linux has 3 built-in tables and each of them has its own chains as follow: FILTER: PREROUTING, FORWARD, POSTROUTING NAT: PREROUTING, INPUT, OUTPUT, POSTROUTING MANGLE: PREROUTING, INPUT, ...
zer0uno's user avatar
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33 votes
6 answers
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We will be deploying a new application to a Server and the application will be listening on port 8443. We have asked Network team to open the firewall for the port 8443 on that server before deploying ...
yottabrain's user avatar
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32 votes
5 answers
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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 ...
cwd's user avatar
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28 votes
4 answers
88k views

How do I set up the firewall on a system in a LAN so that some ports are only open to connections from the local area network, and not from the outside world? For example, I have a box running ...
hpy's user avatar
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