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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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How to open a port to specific IPs in iptables while using docker?

I have a postgreSQL database inside of Docker that I don't want to expose it to the host network as it causes all users to see the exposed database port. (For now I don't have a pfsense or anything ...
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Best way to filter/limit ARP packets on embedded Linux

I have an embedded Linux on some network device. Because this device is pretty important I have to make many network tests (I have a separate device for that). These tests include flooding my device ...
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1answer
24 views

How to prevent iptables and nftables rules from running simultaneously?

I'm trying to set up a firewall on my own desktop (currently I'm tinkering with a Fedora 29 virtual machine). I would like to have it on the "deny-everything-by-default" basis. Almost immediately I ...
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1answer
40 views

How do I find out which process opens a specific port on a specific IP address once in a while?

Once every 5 minutes or so a process on my machine, with my main user id, tries to open a connection to an unknown IP address (no rDNS) at an unusual TCP port (>1k). I can see this in the computer's ...
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2answers
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ipset How to add IP range from x to y

I need to add this 81.212.0.0/14 ip range to ipset. But it doesnt calculate lower than /16. I want to add from 81.212.0.0 to 81.215.255.255 IP addresses. Is there any other way but /14. Im trying to ...
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37 views

iptables to ip6tables

How do I turn my iptables rules to ip6tables rules? I am getting a Bad Address: iptables -A OUTPUT -p tcp -j ALLOW iptables -t nat -A PREROUTING -d 192.168.0.0/24 -i eth0 -j DNAT --to 192.168.255....
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Does routing table work like a per-IP-address firewall, while iptables work like a per-port firewall?

I heard that in a routing table, we can drop packets. Does that work like a per-IP-address firewall to prevent access to certain range of IP addresses from the local device? In comparison, does ...
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23 views

Filter PPPoE packets

Can you somehow inspect PPPoE packets and then filter them with iptables or other tools? PPPoE is below ipv4 so I can't use iptables directly.
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1answer
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Should I remove ICMP Protocol from firewall rules base on security concern?

As you can see from the screenshot of GCP firewall rule page, should I remove ICMP Protocol from firewall rules base on security concern? Will it lower the chance of being attacked? I'm using CentOS ...
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0answers
18 views

Where are iptables rules fetched from while running command 'service iptables save'?

I have created my own file- /etc/sysconfig/iptables-config. On service iptables save my rules are successfully updated and that updates the /etc/sysconfig/iptables file as well. Now even after i ...
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1answer
49 views

Virtualized firewall on KVM

I have few vms (homelab) virtualized with KVM (CentOS7) and connected to my home network. Lately I tried to isolate them by putting them in separate network and I wanted to do so with virtualized ...
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Remote access to a music player from behind a firewall

I'm supposed to set up a broadcasting center at my school. The setup is as follows: a main server (boss) that I have a shell account on (no root tho), with 250mb of free space for my account which ...
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2answers
87 views

How to implement iptables on lxc-container?

I installed lxc-container (fedora 29 amd64) on my ubuntu 18.04 system. The linux container had no firewall command line tools. Therefore I installed iptables into my container and it installed ...
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1answer
313 views

“Not running dhcpcd because /etc/network/interfaces defines some interfaces that will use a DHCP client or static address”

Deployment: VM -- (eth0)RPI(wlan0) -- Router -- ISP ^ ^ ^ ^ DHCP Static DHCP GW NOTE: RPI hostname: gateway • The goal was to make VMs accessible from the outside ...
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1answer
39 views

Firewall software similar to Outpost for linux

I'm corrently using Windows for my machines with Outpost firewall(Agnitum), but want to switch for linux(not sure what disto yet) and would love to know from you what are my options with linux's ...
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1answer
23 views

gufw GUI fails to launch on LMDE

After upgrading from LMDE2 to LMDE3 Cindy I noticed I could no longer launch the gufw GUI. The error was: ** (gufw.py:20536): WARNING **: Failed to load shared library 'libwebkit2gtk-4.0.so.37' ...
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Can't connect to OpenLDAP

i have installed iRedMail with OpenLDAP managing the Mail Accounts. So far that works. Now I wan't to connect other applications to that LDAP and I'm trying to use a LDAP Explorer "LDAP Admin" for ...
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35 views

Limit TCP connections per second for different IP addresses [attacked with 1000 connections with different IP] [duplicate]

How to limit TCP connections per second for different IP addresses? I'm looking for limit per second for different IP's on 25565 port. Limit max connections per IP address and new connections per ...
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1answer
147 views

ssh works only one way

I have two computers, one is running Debian GNU/Linux 9 and the other Ubuntu 18.04.1 LTS. I have installed openssh on both computers. sudo apt install openssh-client sudo apt install openssh-server ...
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1answer
61 views

Routing and filtering on Linux

I have a VM with two interfaces, eth0 and eth1. I would like packets coming in from eth0 to be processed and if they don't match any rule, get dropped. If they match a rule, then I want them to be ...
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46 views

stop the firewalld.service + ERROR: ZONE_ALREADY_SET: trusted

we want to stop the firewalld.service but we get - ERROR: ZONE_ALREADY_SET: trusted so is it possible to erase what is configured in firewall and stop again we have OS - redhat - version 7.3 [root@...
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27 views

Right secure iptabels for a VPN Server?

are these iptables secure for the operation of a VPN server? #ipv4 iptables -P INPUT DROP iptables -A INPUT -i lo -p all -j ACCEPT iptables -A INPUT -p tcp -m tcp --dport 40 -m conntrack --ctstate ...
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1answer
129 views

Ports not really open after firewalld command

OS: CentOS 7 This is a question that is bordering on two issues. I have a docker machine running where I recently installed the PLEX container from linuxserver/plex. The current problem is that I ...
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18 views

How to filter domains on a transparent network bridge?

How can you filter traffic on a transparent network bridge? With iptables it is possible to some extend but most of the time a proxy is recommended or alternatively something like pi-hole or dnsmasq ...
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1answer
41 views

Open port 4000 for Trader Workstation in Fedora

I have installed Trader WorkStation by Interactive Brokers. However, the program does not run, with assistance from support I found that the firewall is the problem. The servers (several primary and ...
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0answers
114 views

Linux bridge SNAT with ebtables

I was reading the following code (dot1x bridge bypass): https://github.com/mubix/8021xbridge/blob/master/scripts/trans_bridge.prepop A quick description, we have 2 interfaces, the first is connected ...
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135 views

Can i use BPF for firewall, instead of iptables

I read somewhere that the BPF is the new iptables, i tried to find how i can i set up firewall like BPF in debian but no luck. You can't use the BPF like iptables ?
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4answers
128 views

setting firewall-cmd --permanent is not sticking after reboot

I have two network interfaces: eth0, and p2p1. My default zone is set to public. I would like to permanently set p2p1 to be trusted. In order the achieve this I run: sudo firewall-cmd --permanent --...
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1answer
69 views

How to apply rules per IP on IPTables?

How can I make these rule apply per IP instead of globally? If one IP sends more than 2 packets per second, all packets for all IPs get dropped, I need it to only drop the packets of the IP that is ...
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0answers
16 views

How to convert USB to ethernet frames and back?

Is there some easy way to convert USB frames to ethernet packets and converting those back to USB frames? The Linux network and USB stack can certainly do the former. That's how USB ethernet / wifi ...
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0answers
26 views

How to inspect and filter USB packets?

I'd like to filter USB packets coming from a USB wifi adapter so that the computer can only see specific wireless devices i.e.the "firewall" would filter out everything coming and going to wifi ...
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1answer
93 views

Ansible orchestration for ufw with ufw --force enable

I deploy an Ansible playbook to some debian:stable machines aiming to update package index cache, install ufw and setup it in the Ansible architecture-agnostic and version-agnostic way. - name: ...
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1answer
172 views

Restrict local port access to a specific user

I'm trying to restrict access to a particular port for a particular user on my Debian. Let's say user's id is 1000 and port I would like to block is 5000. I tried using iptables with the following ...
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1answer
187 views

What is the difference between iptables -S and iptables -L

The help information doesn't seem to be very informative: --list -L [chain [rulenum]] List the rules in a chain or all chains --list-rules -S [chain [rulenum]] Print the rules in a ...
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1answer
36 views

temporarily block outgoing web traffic during work period

I need for a given time period to put a speedbump against my tendency to be distracted by ad hoc web searches while working. I don't want to block LAN traffic because I keep a git server on one of my ...
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1answer
41 views

Firewalld %%REJECT%%

I'm trying to configure firewalld (v0.4.4.2) on Debian 9 to REJECT invalid requests originating from an internal network. However, if I set the default target of the zone in question to REJECT, the ...
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3answers
253 views

UFW is blocking DNS requests through VPN [closed]

I have a very strange behaviour of my UFW on Ubuntu 18.04. I set up basic rules, everything is OK until I connect client to this server through VPN. On the client side ping works fine but nslookup / ...
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1answer
40 views

How do I get a list of the ports which belong to preconfigured firewall-cmd services?

I want to open the following ports in my CentOS 7 firewall: UDP 137 (NetBIOS Name Service) UDP 138 (NetBIOS Datagram Service) TCP 139 (NetBIOS Session Service) TCP 445 (SMB) I can guess that the ...
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2answers
162 views

Mac Address filter in IPtables

I have an application on 2001 Port and i want allow some users with mac addresses to connect to this port. so i use this commands : sudo iptables -A INPUT -p tcp --destination-port 2001 -j DROP ...
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1answer
271 views

How to limit 1 connection per 5 seconds? (IPTABLES)

I want to limit 1 connect per 5 seconds using IPTABLES for people, which are connecting to port "12871/12881". I was trying to find rule for it, but ineffectively. It must be like a "queue" of ...
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1answer
278 views

How to limit 1 connect per 5 seconds? (IPTABLES) [duplicate]

I want to limit 1 connect per 5 seconds using IPTABLES for people, which are connecting to port "12871/12881". I was trying to find rule for it, but ineffectively.
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1answer
168 views

IPTABLES CONFIGURATION CIDR notation

WINPE1 = 192.168.10.5 iptables -A INPUT -p tcp -s 192.168.10.5 --dport 80 -j ACCEPT iptables -A INPUT -p tcp --dport 80 -j DROP iptables -A INPUT -s 192.168.10.5 -p ICMP --icmp-type 8 -j ACCEPT ...
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1answer
243 views

fail2ban with iptables-persistent

I've been running fail2ban for a bit, and recently installed iptables-persistent and am using it with ipset for a blacklist (there's one particular IP that is always hammering away at this machine). ...
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2answers
76 views

Rejecting TCP packets from certain IP on network using iptables

Say I wanted to reject packets that are sent to my computer from a specific IP on the network using iptables. Do I need to define the destination of the packet in my command or is it sufficient to ...
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67 views

Allow localhost connections with VPN

I have some services running as web servers on my PC (e.g., Jupyter Notebook), which stop working when I connect to my VPN through their app (their support team confirmed that this should be the case)....
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28 views

No internet after installing Firewall VPN [closed]

I created a VM and installed debian on it. Everything ok so far. I installed openvpn, tor browser etc. Then my next step was to install the FirewallVPN. After that the internet connection ist gone. ...
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0answers
86 views

traceroute working but telnet time outs with error 28 [closed]

Previously I was able to telnet to a server , but now I am facing timeout error 28. I tried for traceroute it works and shows hopes . I tried below command curl -v -m 5 telnet://ip:portnum I am ...
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1answer
149 views

blocking all traffic except whitelisted ip adresses

I need block all incoming and outcoming connections in firewall, except ip adresses i whitelist. I am currently on virtual machine using ubuntu. I tried these commands from this site: but i cant ...
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0answers
125 views

Purpose of UFW Allow All Rules in FORWARD chain?

What's the purpose of the allow all rules put into the FORWARD chain by UFW? They're currently messing up the 5 ACCEPT rules I've put in place underneath. Unless there's some specific valid reason ...
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0answers
288 views

Can't TFTP GET file on Ubuntu machine from Windows machine

I'm trying download file via TFTP on Ubuntu 16.04LTS machine from TFTP server (TFTPD32) running on Windows 7 machine. On Ubuntu every time I got error Transfer timed out. On Windows 7 PC Windows ...