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Questions tagged [firewall]

a technological barrier designed to prevent unauthorized or unwanted communications between computer networks or hosts

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Ubuntu As a Router With IPSec VPN

I have a network setup with a nonconfigurable hardware firewall that connects a local subnet to my servers at a datacenter - we use Microsoft Remote Desktop Servers and have only stupid RD-clients in ...
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11 views

How to seed torrents in Linux?

On my laptop I managed to open the port, which I am using in Transmission and QBitTorrent. I open the port with the following command : sudo iptables -I INPUT -p tcp --dport 9000 -j ACCEPT, then I ...
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1answer
33 views

what port should be allowed in ufw to allow specific outbound traffic and why - SPT vs DPT

I am having trouble understanding how SPT and DPT translate for outbound connections. When ufw blocks a certain outbound connection, which is the port that needs to be unblocked and why. For example, ...
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26 views

status ufw problem (exited)

I have a problem with the ufw (firewall) program that is running, but status is "Active: active (exited) since Wed 2019-02-13 14:56:25 +0330; 31min ago" can anyone help me the reason?
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34 views

SSH Failing between my Jenkins server and my web server

Ok, so recently I started noticing, basically the last week, that my Jenkins server has been intermittently failing builds due to an ssh timeout. This has gotten progressively worse until now, where ...
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41 views

Allowing VPN traffic trough Ubuntu firewall to connect on Sophos firewall

I need advice to achieve something and I can't find the answer anywhere. I'm setting up a network in a test lab. I have an Ubuntu machine that runs SNORT as an IDS and it's the only machine that as ...
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1answer
57 views

How to check UFW status without sudo (or being root)? [duplicate]

I'm running some scripts to check the UFW status and would like to run sudo ufw status without having to do sudo. I was hoping to find a firewall or ufw group to add myself to, but I didn't find any. ...
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23 views

Internet not working with “Home” profile in Firewall

Recently my Internet is not working after selecting the "Home" profile in Firewall configuration. If I select "Office" Profile, then Internet works.Is there any issue if I select Office profile on my ...
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2answers
66 views

Strange new rules added to my iptables config… Was my server hacked?

Today, I listed my iptables for a routine check -- and discovered two strange UFW rules that I don't remember setting up myself, referring to two specific IP addresses that I can't identify: -A ufw-...
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1answer
18 views

emails for all denied network activity using ufw

I have ufw configured to deny all incoming and outgoing traffic except input for SSH: ufw default deny outgoing ufw default deny incoming ufw limit in ssh Is it possible to get e-mails of denied ...
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0answers
18 views

Allow inbound traffic on port 80 Ubuntu 18.04 on AWS

I've setup an application running locally, then route traffic from port 80 to it using nginx. When I log into the server I can see my application running perfectly at localhost on port 80. On AWS I'...
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1answer
37 views

Understanding UFW log

What does this UFW log mean? Has already asked this question, however he asked it with a specific intention and the log in actuality did not get covered in the answer. Therefore I did not benefit and ...
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35 views

ssh connection refused, port listening, process running, IP address not banned

$ git pull ssh: connect to host HOSTNAME port 22: Connection refused This only happens when the client is connected to one specific wireless network. If I connect from a wired connection (even in ...
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26 views

Issues with OpenVPN server accepting connections but not allowing traffic

I have installed Ubuntu 16.04 on a rooted Android box with Linux Deploy to make it a OpenVPN server. I have diligently followed the guide at https://nanashi07.blogspot.com/2017/...id-device.html and ...
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0answers
27 views

Port Forwarding for Minecraft Server Not Listening

I am trying to setup a ip server for minecraft bedrock and I am having issues with port forwarding not being open and it says connection timed out. I seems to me that the program is not "LISTENING". ...
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1answer
63 views

Getting IP whitelist of repo servers (Ubuntu 16.04)

We have various Ubuntu appliances deployed throughout the US. We've run into some situations recently where we are getting requests for IP whitelists (instead of FQDN whitelists) of the repos that we ...
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1answer
28 views

Unable to open port

I try to convince apache to listen to two ports (80 and 8091). That works perfectly locally. I configured iptables so that port 8091 is shown as follows using iptables -L Chain INPUT (policy ACCEPT)...
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1answer
29 views

Make ufw follow iptable rules

I have a bunch of configuration in ufw that I want to avoid porting to iptables (unless there is a easy way to export from ufw and import in iptables). Simplicity of ufw etc. being the reason. Now I ...
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46 views

Whitelist GoogleUpdate.exe in Firewall settings on Ubuntu system

I am trying to install Google Drive's 'Backup and sync' on my Ubuntu 18.04 but as this is not available for Linux systems. I am using Wine to install Window's exe file. So while running the exe file, ...
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65 views

change filtered port to open

Basic Question: How do I change a port from filtered to open so that I can call nc to view data over a port? Information: I have a program that posts data to port 50000. I can run the program fine ...
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1answer
89 views

Cannot access local server with IP address while localhost and 127.0.0.1 can

I am trying to let other computers to access my local server but I tried myself locally that I cannot access it locally even myself. Several things you should know: My target Visit my server via ...
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0answers
40 views

I can't make the external IP input connections on my Ubuntu Server 18.04 LTS

I installed my Ubuntu 18.04 server and configured it with static public IPV4, it's work!! but I can not make incoming connections through external ips, just the same network as the server, but the ...
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44 views

UFW Specific rule per IP

I have two ips on my machine, 193.70.80.99 and 51.68.55.231 I want to open port 22, 80 and 17071 (tcp) for 193.70.80.99 And open port 25565 (tcp) for 51.68.55.231 So that the 51.X ip cant be used ...
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1answer
23 views

Map a range of ports to another range of ports (equal lengths of ranges)

In this answer, How can I open a range of ports in ubuntu using (g)ufw, a simple command for opening a range of ports is given. For example, using this command I can open the ports 1000-1999 very ...
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0answers
48 views

UFW failing to start at system boot, but manual enable works

Whenever I reboot my server, UFW will refuse to come up, with the following error messages being visible in systemctl status ufw.service: Dec 21 02:02:39 ironwolf ufw-init[503]: iptables-restore: ...
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1answer
71 views

firewall and virus protection [closed]

I am new to ubuntu 18.04.1 lts it says that( A built in firewall and virus protection are avaliable) it says to go to activities left payne but there are no icons there for firewall or virus ...
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69 views

Ubunu Server KVM: Sophos Firewall

I am running a Ubuntu Server with KVM. The machine uses 8 physical NICs. Currently i am in a learning and testing state (so please correct me if you see errors): I have 1 VM running, which is Sophos ...
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1answer
209 views

Protecting WSL-Ubuntu and WSL-OpenSSH (unfiltering port 443 correctly, to use just these)

I use WSL-Ubuntu on Windows 10 home (build 17134.472) basically just for OpenSSH and Ansible and AFAIK both require only port 443 to be unfiltered to work properly. I have both Windows Firewall and ...
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1answer
135 views

I can't use ufw on WSL-Ubuntu

I use Windows 10 home (build 17134.471) with WSL-Ubuntu 16.04 (xenial). I executed apt update -y && ufw --force enable and got the following trace (I don't know what it means - maybe some ...
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0answers
50 views

How would you troubleshoot: Transmission port test fails despite port being open. Unable to download torrents

Recently started having trouble with Transmission, worked fine before. But now it just never starts downloading the torrents. I went to see if maybe it was a firewall issue so I looked in preferences ...
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1answer
56 views

iptables prevents me from connecting

I'm using Ubuntu 18.04 and my current iptables rules are from this question; iptables -L gives: Chain INPUT (policy DROP) target prot opt source destination ACCEPT all ...
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126 views

Does Ubuntu now use bpfilter or netfilter?

I'm trying to put together a firewall/router using netinstall of Ubuntu 18.10 with bpfilter. I know it's packaged by default with kernel >=4.18 these days, but I'm a little confused about how to ...
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18 views

Restrict access to web application using UFW firewall [duplicate]

How can I use UFW to restrict the access to a web application (port 80) so it can be accessed only by specified IPs?
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2answers
100 views

How to Limit Connections to 1 connect on 5 seconds? (IPTABLES)

I lead server in game, which have broken AntyCheat and if there are many connects in one time it break whole server and no one can connect. So the solution for it is limit connections in one time to 1 ...
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0answers
53 views

Unable to connect (IPv6)

I couldn't find an answer or solution to my question in existing questions/answers on the net, so I have to write down my problem hoping that some expert spots the problem. Anyway here it goes. I ...
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0answers
30 views

Allow localhost connections with VPN

Note: Cross-posting from Unix & Linux since the question got no replies there. I have some services running as web servers on my PC (e.g., Jupyter Notebook), which stop working when I connect to ...
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1answer
2k views

UFW: what exactly is it?

What is UFW? You would think this is an easy question, but the more sources I read, the less clear it gets. The acronym spells out to Uncomplicated FireWall, as though ufw actually implements a ...
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1answer
20 views

Apache2 does not work, but syntax is OK

I installed apache2, but it doesn't work. I also allowed it in ufw. The output in terminal after sudo apache2ctl configtest is "Syntax OK". I am using Ubuntu 16.04. What can I do?
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45 views

I can ssh via port 42043, but not via port 7999 (connection refused)

I have the following setup in my ~/.ssh/config file: Host atlas user dci HostName <redacted> Port 42043 AddressFamily inet GSSAPIAuthentication no I can connect to ...
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20 views

Iptables - security setting

I going to use a Ubuntu laptop on a public WiFi network, probably with full of hackers. What iptables rules would you recommend? I don't mind blocking NTP port 123 for security. I just use my ...
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0answers
28 views

Can ssh local but cannot from other computeres

My desktop is a Linux (Ubuntu) machine with ssh server configured. It used to work fine before I moved the desktop to a new network. Now I can ssh into the machine from itself (either by ssh localhost ...
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1answer
45 views

ssh connection times out

I have 2 Ubuntu servers that I access via their IP addresses, which are named bris (running Ubuntu 14.04) and syd (running Ubuntu 18.04). When trying to connect from syd to bris I get: root@prod:~# ...
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1answer
87 views

Trying to write the perfect VPN kill-switch bash script - have a question about wlp3s0 traffic. Ubuntu 18.04

I recently started using Nordvpn which advertises that it has a kill Switch feature that supposedly will kill all traffic if it loses the VPN connection. After some experimentation I found that the ...
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1answer
56 views

iptables rules applied multiple times

I had a very simple set of iptables rules on a newly installed system: $ sudo iptables -L Chain INPUT (policy DROP) target prot opt source destination ACCEPT all -- ...
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0answers
245 views

How to open port 22 with iptables

I am not able to ssh into an ec2-instance. when I run nmap -Pn 10.xxx.xxx.xx I see that instance doesn't have port 22 open I have a security group added to this instance that has a ssh rule added. I ...
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2answers
2k views

Ubuntu 18.04 Login window loop

Is there any reason the login window would stop working and start looping? I'm running 18.04. I normally RDP into the ubuntu box, but that isn't working now. Using a keyboard and mouse, I see my ...
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0answers
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How to block sending of SNMP broadcasts to the network?

Our administrators notified me that my machine is bothering the corporate network with SNMP broadcasts. I suspected CUPS, removed all printers from the config and tried everything shown here: How do ...
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3answers
5k views

Ubuntu 18.10 stuck on “Started bpfilter” while booting

Today I have updated from my Ubuntu 18.04 to 18.10 by software upgrade app ( coudn't wait till tomorrow 😆). It took a bit of time, but at the end of it I was asked to restart my PC. Upon restarting, ...
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0answers
37 views

Why have commands ip6tables, iptables or ufw no effect?

I want to block a certain ipv6-address and this is somehow rejected (by object?)? Command is: sudo ip6tables --policy INPUT fe80::da58:d7ff:fe00:8d0c -j DROP ... and this has no effect. Is this ...
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1answer
38 views

Where is to edit the firewall-rules for iptables and ip6tables correctly?

I want to set myself up the rules for firewall in iptables. But several queries have delivered different file-locations for iptables-rules. One location is in /usr/local/bin and there is to create ...