Questions tagged [firewall]

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 forward port traffic to another port with byte calculation

Problem I want to 'redirect' traffic from one port to another. But I need to be able to calculate how much INPUT AND OUTPUT bytes were used in communicating through that port. Half Solution iptables -...
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Blocking outgoing requests to specific domains e.g. facebook, twitter

I'm finding that Firefox and Chromium are both ignoring my /etc/hosts file. Is there a way for me to block all outgoing requests to a particular set of domains e.g. Facebook.com and Twitter.com. For ...
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Only KVM Guest Should Have Access To Internet

My setup has one server which also acts as the KVM host. Everything is built on Debian Buster, running several services for local use (networks 192.168.x.0/24). There are several wired network ...
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iptables DROP policy on INPUT causing 10+s of latency in SQL responses

I am trying to lock down my db server but have encountered something I cannot explain. Chain INPUT (policy DROP) num target prot opt source destination 1 ACCEPT tcp -- 0.0....
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My /etc/hosts is having no effect

I added a large number of domains to my /etc/hosts, in the hope of preventing outgoing traffic to those sites. Now I have found however that my /etc/hosts is having no effect. It's meant to serve as a ...
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1answer
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Nftables default drop chain problem

I'd like to take a default drop approach to my firewall rules. I've created some rules for testing purposes: table bridge vmbrfilter { chain forward { type filter hook forward priority -...
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firewalls, PackageKit, and cripplingly slow wireless throughput (oh my)

I'm a bit out of my element here, as network operation and security aren't something I have much experience with. My question relates to abysmal internet speed (speedtest results in 1Mbit down / '...
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How do I list out ports in a specific format?

I would like to print ports, their status, and what program is running on them in a format like this: port#:portStatus:program in order to make a script that can ask me if I would like to make a ...
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1answer
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iptables recent module: remove entries older than

I am using iptables recent module: -A INPUT -m recent --rsource --name PORTSCAN --set -j DROP The above line adds offending IP addresses to /proc/net/xt_recent/PORTSCAN. Now I am looking for a way ...
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Stop ISP firewall

I've set up an apache web server with port 80, I can access it very easily within the network by typing the IP x.x.x.x:80 in the browser (I know that I don't need to specify the HTTP port). However, ...
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UPnP with firewalld

This question is probably related to: Fedora firewall with UPnP? Because newer fedora workstations use firewalld, it's a bit of a different situation. The problem I'm experiencing is that I can't ...
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Disallow port in URL when using reverse proxy

I want to run a reverse proxy, using nginx. My setup consists of one root nginx server (aforementioned proxy) and two other nginx servers that are in docker containers (with already exposed ports to ...
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accessing tcp port inside guest os

I would like to access a port on my guest OS from my host OS. I am using 127.0.0.1 on the guest OS since my database is also in that network, and since I just now understood(while it was right in ...
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IP Tables - Blocking Incoming Traffic

This question is in a way related this and this My question is about blocking incoming connections using iptables. I read different posts in unix.stackexchange.com and got a basic understanding of ...
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1answer
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block all VM connections but forward to a single host

I want to restrict internet access of a virtual windows machine. I want this machine to be able to reach a certain IP address and upload/dowload files from this server. I set up an OPNsense ...
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1answer
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iptables forward some devices to different interfaces based on source IP

I'm trying to expand further on a recent question I had asked here (and was helped) based on this tutorial: https://www.instructables.com/Raspberry-Pi-VPN-Gateway/#step5. Using a Raspberry PI as a VPN ...
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unbound-anchor and strict DNS-firewalling

I have a strict firewall policy in my local router for DNS-ports. I only open for certain DNS-servers and want to keep it that way. Lately, I have been trying out unbound. It works fine but there is ...
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UFW rules not working as expected

This is how the UFW configuration looks like in my Raspberry PI Status: active To Action From -- ------ ---- 1194/tcp ALLOW ...
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1answer
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iptables does not block forwarding to another IP of the host itself

I have host used as gateway with net.ipv4.conf.all.rp_filter=0 and iptables rpfilter that is used instead iptables -t raw -A PREROUTING -m rpfilter --invert -j LOG-DROP-RP My host have 2 interfaces ...
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Ubuntu 18 VM deployment with the firewall already disabled

What exactly do I add into the cloud_init.cfg file to have my Ubuntu 18.04.2 VM(s) deployed with the firewall already disabled since inception? Also what (permanent) changes do I make in already ...
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iptables / route for returning incoming traffic back out of originating interface (eth0)

I'm just getting started with tinkering with Linux / IPTABLES and following this great tutorial here to successfully setup a RaspBerry Pi device (running RaspBerryPi OS / Debian) as a VPN Gateway. Any ...
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Converting an add-rule to a service for firewalld

I am having a hard time creating the following lines for multicasting into a service in firewalld. firewall-cmd --permanent --add-port=49152-65532/udp firewall-cmd --permanent --direct --add-rule ipv4 ...
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iptables: drop any ip not on whitelist, short circuiting chain

I have a whitelist of ip addresses I'm storing in a ipset. I want to craft an iptables rule for my input chain where any IP NOT on the whitelist gets dropped immediately and no rules further down the ...
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UFW firewall preventing updating packages even with less restrictive rules

I'm using UFW version ufw 0.36, on 20.04 Ubuntu. Now i noticed that, by using: ufw allow out http ufw allow out https ufw allow in http ufw allow in https ufw default deny incoming ufw default deny ...
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Forward SSH traffic from public IP to local IP

I need to find a way to forward ssh traffic from a WAN ip address to a specific host IP address on a local network. The set up is as follows: WAN ---------|Firewall| ----SSH Machine EXTERNAL | ...
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Cannot cUrl self with public IP

My home network has a CentOS based server connected to it. I have a router, where the 80 and 443 ports are forwarded to that server. I can reach this server with the public IP of the router and ...
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How does inbound port blocking work on a firewall?

Something is unclear to me about inbound traffic and firewalls. My first assumption is that a firewall - say for a home router - should block all inbound ports. If you don't block all inbound ports, ...
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How to properly log and view nftables activity?

On Debian 10 buster I am having problems with docker containers unable to ping the docker host or even docker bridge interface, but able to reach the internet. Allowing access as in related questions ...
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OpenVPN block users established connection?

following scenario: I have clients connected to my VPN who are using a specific app that is using UDP Port 54477. However I want to block that connection during the night (ex. from 0-6). So I want to ...
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block port while its already being used?

let's say I have a program running that is already using a random tcp/udp port. If I deny connections now via iptables/ufw the port is still open for that programm until I close/reopen it. Is there ...
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Qemu network traffic filtering with iptables

I need to filter both outcoming and incoming traffic of the guest system on Qemu (Linux). The host system is Linux too. I think iptables is a good tool, but I don't know how to use it here. What ...
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IPTables is blocking all outgoing traffic to http even though I allowed it

I am using the following code to allow DNS requests, and outgoing traffic to port 443, 22 and 80 However, all the traffic to port 443 and 80 is blocked for some reason # Allowing DNS lookups (tcp, udp ...
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UFW kills SSH access on reboot

I'm trying to block all connectivity except what's required for a SSH server to function using the following commands on a freshly installed ubuntu 18.04 server: sudo ufw allow ssh sudo ufw default ...
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Why is it that TCP packets can be modified to block invalid packets, but not UDP packets

On a random day I was googling iptables rules to harden my desktop, and came across this post[1]. At some point the guide mentions blocking invalid TCP packets using tcp-modules with these rules; ...
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Iptables rules script problem

I found this script online, but there are 2 problems after executing on linux mint: No internet from USB WiFi adapter, only from internal wifi Can not connect to any VPN What do I have to change ...
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smbstatus --shares returns no shares

Issue: I am trying to set up a Centos 8 samba share to be viewable on Arch + Windows I am new-ish to linux, but completely new to Centos, I set up a server and set up samba from this guide: https://...
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How to set up apache server for public domain on linux?

I am running Arch Linux on my computer. tl;dr I have portforwarded apache and the router on port 80 and disabled all firewalls on my computer and router. Apache has started and started with no visible ...
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How to: Linphone network ports for firewall

After some experimentation, I have found that the following ports need to be opened on the host firewall: Linphone dynamic port range: 10000-17000 (I have not seen anything yet outside of this) ...
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1answer
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Modifying firewall rules with pfctl on NetBSD 4

I'm wanting to modify some firewall/NAT rules on a device (Apple Airport) running NetBSD 4.0. I'm not that familiar with BSD and pf, so want to check the right approach. I can change the pf.conf file (...
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kernel modules missing

I'm using this NPi i.MX6ULL (armhf) board here. It comes with a customised linux distribution, based on Debian Buster. But it's been completely stripped down to the bare minimum. My question isn't ...
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Setting up a Debian Firewall (with UFW) on a bridge connection (wi-fi) — Broken pipe ERROR

Good morning, I'm currently working on the creation of a web server. Here is my setup : MacbookPro running -> VirtualBox VirtualBox running -> Debian 10.04 (only command line) Docker with -> ...
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firewall-cmd open port issue

I have CentOS 7.7. I try to open port 9001 by the command: firewall-cmd --zone=public --add-port=9001/tcp --permanent & firewall-cmd --reload' I can see the port in the command firewall-cmd --list-...
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How do I open firewall for NFS server on OpenSuse Tumbleweed?

When I disable the server firewall, the exported directories appear on the NFS client. Otherwise they don't. I've tried allowing the 'nfs' service on both the "public" and "internal&...
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Using qemu/kvm with nftables? (without firewalld!)

With libvirt/qemu/kvm you can define a bridge (or more) to be used by the guest machines. The libvirt machinery should take care of the creation of the bridge - normally called virbr0 with virbr0-nic (...
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2answers
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iptables - Drop NAT rules based on rule/name, NOT rule number

I need to script some Iptables rule changes involving NAT rules (-t nat) on Ubuntu 16 servers. It seems like the common way to drop a rule using -D [rule here] does not work with the -t identifier... ...
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How do I see how much CPU time my firewall uses?

I was attacked with a DNS Amplification and as a result added nearly 4,000 IP addresses to my firewall using fail2ban. I have seen many people worried about how many rules they include in their ...
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135 views

Forward debian LAN to another router without nat

Is it possible to create network forwarding through debian without using nat? I have the following network structure. ip: xxx.xxx.xxx.xxx/xx ---- Internet - wan - [Router with nat] --- lan (10.1.1.1/...
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Securing private network during port forwarding?

If I open port to a single server on a private network, will that put every computer in my network at security risk? For example, if I have a company desktop and allow ssh into that desktop from a ...
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How to safely allow particular remote IP access to particular servers on private network?

I have HPC that I want people to use it remotely without giving them access to other computers in the private network. Other computers are operating on network. I am using port forwarding. sudo ...
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2answers
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Centos 7 firewall is blocking file exchange

My Centos 7 firewall is blocking file exchange (import and export) with an external FTP client if I try to connect via script. Everything works fine if I disable the firewall. Do you know if a ...

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