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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Is there a simple gui application-firewall for linux? [on hold]

I have tried installing Douanne firewall, but I faced problems in installing it ;there are dependency problems. I tried Peerblock but there doesn't seem to be a way to actively pop up a dialog saying ...
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3answers
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iptables: allow certain ips and block all other connection

How do I allow certain ips and block all other connection in iptables?
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1answer
305 views

Permanently start the OpenBSD pf Firewall on OS X

I use Mac OS X El Capitan 10.11.3 at the desktop OS. As everyone knows, is Apple's Mac OS X built on FreeBSD! I use normal only Debian/GNU/Linux on desktop and OpenBSD on Server and Firewall: So my ...
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4answers
496 views

Is it possible to simulate “no external access” from a Linux machine when developing?

Sometimes I upload an application to a server that doesn't have external internet access. I would like to create the same environment in my machine for testing some features in the application and ...
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0answers
25 views

Blocking incoming connections from external ports

How can I block incoming connections from some port which exists on some internet server, not on my PC? I tried to do it by rule <port> DENY IN Anywhere in gufw firewall, but it looks like it ...
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0answers
22 views

Why does mounting external harddrive trigger a UFW event?

Today I noticed when I plug in my 2TB external Toshiba hard drive, it triggers a ufw event in my logs: Jul 20 11:24:20 linuxbox kernel: [152873.728277] [UFW BLOCK] IN=inet1 OUT= MAC= SRC=xxxa DST=...
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1answer
26 views

What are the most restrictive external firewall / DNS listening port settings I can have for my DNS server (internal clients only)

This question relates specifically to hardening the configuration of DNS, firewalls and at the limit, ntp. (not proxys, http access,vpn's or other services). This is about the externally-facing side ...
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2answers
58 views

Fedora 24: ports show as open when scanned from server, but closed when nmapped from outside

I have a Fedora 24 server, serving an Angular2 project. Angular2 automatically opens ports 3000 and 3001 once the service is started. However, although running nmap localhost shows the ports are open, ...
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1answer
47 views

Freebsd: pf firewall doesn't work on restart

I'm running FreeBSD 10.3 p4 and observed some strange behavior When restarting the machine pf starts due to /etc/rc.conf entry # JAILS cloned_interfaces="${cloned_interfaces} lo1" gateway_enable="...
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1answer
9 views

How to investigate routing of firewall issue?

SERVERA needs to reach SERVERB. we cannot ping SERVERB from SERVERA. we cannot see any open port for SERVERB from SERVERA. Question: in general, how can we find out, that it is a routing or ...
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1answer
27 views

linux + iptables + /etc/sysconfig/iptables

on my linux machine I see the following: iptables -L Chain INPUT (policy ACCEPT) target prot opt source destination Chain FORWARD (policy ACCEPT) target prot opt source ...
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3answers
374 views

Build my own firewall, in Java or other high-level language?

I posted a question on ServerFault about a specialized Firewall setup, but as an avid software developer I am also considering rolling my own. I am only interested in using a high-level language, ...
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1answer
107 views

How to completely block ssh and pings to server running Oracle Linux 6.7

We are facing IP abuse issues and want to completely BLOCK ssh and ability to ping our servers running Oracle Linux 6.7 and only allow vnc connections. How to achieve this using linux firewall or ...
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0answers
14 views

convert openwrt rules to ubuntu 14

I have the following rule for openwrt firewall & network. Can anyone convert this to ubuntu 14? from /etc/config/firewall (openwrt) to ubuntu 14 command line: config ipset ...
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1answer
2k 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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3answers
111 views

preventing DoS attack in Apache webserver

This is the version of apache we're using - httpd-2.2.15-39.el6.centos.x86_64 We recently had our website down due to DoS attack and hence started exploring iptables, and how to use it to prevent DoS ...
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1answer
1k views

Corosync & Pacemaker IPTables Rules

When using Corosync with two rings via multi-cast addresses 226.94.1.1 (Port 5405) & 226.94.1.2 (Port 5406) what iptables rules are required to allow two nodes to communicate optimally without ...
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1answer
13 views

UFW app based filtering

is there any filtering in ufw which works sort-of like win firewall? basically allowing me not only to create ip/port/proto based rules, but also to bind such limitations to specific executables ...
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1answer
4k 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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3answers
256 views

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
46 views

Domain only for web server

I have a domain which I want to point to my server. But I don't want to allow other people to use this domain to reach the server, only specific ports on the server (web server, so port 80). So if ...
1
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1answer
57 views

How would I limit connections to certain services, to be only accesed via a connection coming from a sub-domains?

I have a personall machine running Ubuntu 14.04.4 LTS. I use it to host a Teamspeak and a Minecraft server and also a website. I am trying to make sub-domains to only point to the right services. So ...
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0answers
102 views

Which iptables chain does a new stream created by TEE go to?

Where do packets go after being created by the TEE target? I am working on mirroring some traffic that needs to go to multiple computers on my network. So what happens to both streams after using ...
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1answer
46 views

iptables configuration

I'm trying to setup iptables, the forward rules are workin fine, but the output rules are making problems. I Can't access internet from the hosts beheind the firewall neither the firewall server can ...
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0answers
14 views

WLAN with multiple unique users

Following use case: There are 6 holiday apartments which all use the same WLAN. After a preceding law case due to illegal downloads every apartment needs to be monitored for eventually following ...
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1answer
48 views

Block countries based on IP in firewall

I would like to restrict visibility of my server from outside my country. I am connecting to my personal server always from one or two countries. Is there a way to block all the IPs coming from all ...
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1answer
40 views

Shorewall 4-interface setup

I am trying to use shorewall on Arch to manage a setup with 2 local networks and 2 ISP connections. Ultimately I want traffic from local network 1 (192.168.1.0/24 interface enp5s0) to use ISP 1 (76. .....
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2answers
2k 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
50 views

Why “echo f” in the case of clearing conntrack table doesn't work on debian?

Many people don't clear the conntrack table when they want to reload their firewall rules. When you have some ESTABLISHED connections, all the sessions won't be affected when you add a rule that ...
3
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1answer
70 views

Add route from internal network to external network

I am using a box running Arch as my router and firewall (with shorewall). Recently, I tried to add another network onto the system, which failed horribly. After putting everything back where it was ...
2
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1answer
577 views

How would I go about getting UPnP working on a Slackware server/firewall?

I'm a long time fan of Slackware and I've always had a machine serving as my main server/firewall with the latest version installed. I have it now but I'm struggling to find information on how to ...
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1answer
900 views

How does KVM set its own netfilter rules?

I've been poking around with KVM VM's on Centos 6.4 not having an internet connection on my VM's, I found something curious: Upon booting the machine, iptables has rules in the FORWARD chain to allow ...
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12 views

DD WRT restrict access but exclude subdomain

I know it's possible to restrict access to some websites in Access restrictions section. I'd like to know if it possible to exclude from restriction subdomain of a site. For example: http://...
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1answer
101 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
30 views

iptables connection mark not balance

The following is my network topology: + + | | | | | | | +-----------...
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1answer
96 views

how to find out which chain in iptables in listing

Suppose I have the following two entries line of iptables: iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE iptables -A INPUT -s 192.168.1.0/24 -j DROP So, I have POSTROUTING and INPUT chains. ...
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1answer
401 views

pfsense: No more processes

Sometimes my pfsense (1.2.3-RELEASE) goes crazy: every nat rules go down the web interface reply me with many errors (Warning: shell_exec(): Unable to execute...) my ssh daemon refuse to open a new ...
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1answer
110 views

iptables rule explanation

I was looking to update iptables in our webserver which would prevent DoS attack to an extent. 1) Related to web traffic, below are the iptables rules i found. iptables -I INPUT -p tcp --dport 80 -...
7
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1answer
992 views

Opening port 80 but remain secure

I have a standard installation of Ubuntu 10.04, and have installed the LAMP stack so I can do some web development locally. On my router I have opened port 80 so I can develop with external services ...
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38 views

Unable to access http server when ufw is running, on Raspbian?

I have a Raspberry Pi running Raspbian, with Apache2 for the web server. Some recent change seems to have broken my ability to access my web server, when ufw is running. The server simply doesn't ...
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1answer
31 views

Understanding Iptables rules to prevent DDoS

Following IPTables rules exist on my system as some preventive measures against DDoS attacks -A INPUT -s 255.0.0.0/8 -j LOG --log-prefix "Spoofed source IP" -A INPUT -s 255.0.0.0/8 -j DROP -A INPUT -...
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0answers
53 views

Why fail2ban doesn't put some IP address in jail

This is several days ago, I observed some IP addresses was't banned by fail2ban, and continued to brute force attack on different port of ssh. This an extract of my logwatch: undef: 22 times a [...
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1answer
77 views

How do I make sure the iptables is closed?

I want to disable iptables completely. I followed the instruction like /etc/init.d/iptables close it said there No such file or directory [root@dataapp02 tmp]# service iptables stop Redirecting ...
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3answers
65 views

IPtables installation question

I am new to installing iptables and have an excellent book called "Linux Firewalls: Attack Detection and Response" by Michael Rash. I have a few questions before I begin. I want to make an ...
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2answers
124 views

Packet flow in a virtual bridge with two interfaces, centos 7

I am struggling to create a bridge firewall with iptables since I cannot find/catch packets flowing through a bridge with two interfaces in centos7. No ip addresses are configured on interfaces or the ...
3
votes
1answer
189 views

What ports need to be open on a firewall to access the internet?

Let's say as the example that I have a firewall that blocks ALL ports from all sources/destinations. What ports would I need to open to be able to successfully run: ping google.com ...and are ...
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2answers
49 views

Access to the internet from a firewalled server

I'm trying to set up a test Docker platform at work. I need pull images, but can't do so because the test server does not have direct internet access (firewalled). There is another server that can ...
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0answers
13 views

pcfl - Allow ssh for an specific IP

I'm working with pfctl on Mac OS X. Im trying to make a policy/anchor what blocks SSH for ALL ips, minus specific ip. I try this: pass in on fxp0 proto tcp from any to any port < 22 flags S/SA ...
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1answer
1k views

pf blocks all in/out traffic instead of just the one port I wanted to block

I need to block one incoming port with pf. I'm new to pf, and I can't figure out what I'm doing wrong here. Here is my entire rule file, made to block incoming port 22: set block-policy drop pass in ...
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3answers
59 views

iptables: block all inbound traffic over a certain port number

It is possible using iptables (on Debian) to block all inbound connections for all the ports with a port number over (as an example) 16000. Like this (using 16000 as reference): The port 15999 is ...