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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3
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1answer
173 views

Proper way to handle FTP over SSL with restrictive firewall rules?

Without SSL, FTP works fine over a stateful Firewall, like netfilter (iptables) + the nf_conntrack_ftp kernel module like this: # modprobe nf_conntrack_ftp # iptables -A INPUT -m conntrack --ctstate ...
-2
votes
1answer
113 views

How can I tease Sonicwall ?

In my college, I can't use the web, because they use Sonicwall network firewalls How can I tease it? For I use all websites in my college? Please see the result when I access a website blocked ...
0
votes
1answer
72 views

Linux hosts.deny settings are not applied

I want to make a bunch of websites unaccessible on my computer. My hosts.allow file: sendmail: all # /etc/hosts.allow: list of hosts that are allowed to access the system. # See ...
0
votes
1answer
65 views

how to find out wich 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. ...
3
votes
1answer
2k views

Configuring OpenVPN to use Firewalld instead of iptables on Centos 7

I need some help configuring OpenVPN on Centos 7 using firewalld. I used iptables on Centos 6.5 and only had to add the following lines to /etc/sysconfig/iptables: -A POSTROUTING -s "10.0.0.0/24" ...
0
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0answers
78 views

How can I use 0.0.0.0/0 in ipset hash:net,port?

Right now, if I do ipset a ansible_allowed 0.0.0.0/0,tcp:22 I get ipset v6.19: The value of the CIDR parameter of the IP address is invalid and instead I have to add 0.0.0.0/1,tcp:22 ...
3
votes
1answer
109 views

IPTables rules for specific processes [duplicate]

I have a lot more experience with the Windows Firewall with advanced functionality than I do with IPTables. With the WFAF, I was able to lock down a program so that it could only connect over specific ...
1
vote
1answer
284 views

Curious about strange ICMP type 3 code 10 traffic to my IP address

My firewall (iptables) logs some strange ICMP type 3 code 10 traffic that I am curious to understand (specifically how or if this could be an exploit of some sort). Type 3 = Destination ...
1
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0answers
58 views

How to debug the network issue in case of blocked database connections

I am trying to understand if my analysis of the below information is correct. For all the 3 scenarios listed here, port 80, port 3306 and port 22 are open in the server's firewall. Also, for all the 3 ...
2
votes
1answer
607 views

Unable to access website hosted on virtual machine

I'm on a mac (osx 10.9.3) running CentOS7 in virtualbox. I would like to access the website hosted on the virtual machine. Browsing to the Guest IP returns webpage not available. I'm able to ping and ...
9
votes
2answers
4k views

( /etc/sysconfig/iptables ) “Manual customization of this file is not recommended.” Why?

Editing this file directly /etc/sysconfig/iptables can save me so much headaches so much time and so on... and yet on the very top of the file it says.. Manual customization of this file is not ...
0
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1answer
85 views

Is it OK to copy /etc/sysconfig/iptables to another machine?

This is my original server with very loose security given that it does not block all ports via iptables. /etc/sysconfig/iptables contents: # Generated by iptables-save v1.4.7 on Mon Jun 16 ...
1
vote
1answer
29 views

Software firewall with “zone files”

I am using an automatic deployment system for my new Unix deployments. I have a fairly complicated network topology to implement, and I'm looking for firewall software that makes this easy. In ...
1
vote
2answers
92 views

Reject ssh connections made from proxies

I was seeing this question which was concerned with blocking access to the users who do not belong to a particular region. I am sure that blocking is possible but I see there is a workaround to this. ...
2
votes
0answers
27 views

How to build an equivalent of littlesnitch or zonealarm under linux? [duplicate]

The question : Recommended reverse firewall applications for linux? asks for a reverse firewall used to monitor, preventing or permitting network access, at the process level, with a GUI. There is two ...
8
votes
6answers
268 views

iptables rule adviser script

There is a server without any iptables defense: ACCEPT all.. There could be custom applications on this server. If we should need to harden this server (so deny all, and only let what is needed by ...
0
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0answers
194 views

Unable to SSH into Puppy Linux, even though SSHD is running

I installed OpenSSH client and server on my Puppy Linux computer. That computer is behind a router. I tried to ssh into it over the internet (outside the router) but it times out. Also doesn't work if ...
2
votes
2answers
164 views

Temporary redirect ports

I need a temporary redirection of some ports to another machine. I've tried: iptables -t nat -A PREROUTING -p tcp --dport 4321 -j DNAT --to-destination 192.168.121.4:80 But shorewall blocks all ...
1
vote
0answers
99 views

How do I control ip routing in the new firewalld?

I have the following scenario: Our fedora server is connected to the internet on eth0 and has a second nic, wlan0 acting as an access point. The purpose of the access point is to provide a connection ...
2
votes
2answers
580 views

How to do domain filtering in Linux?

Preferably something similar to iptables. Basically, I want to do domain filtering/whitelisting/blacklisting like I would with IPs in iptables. Are there any recommendations on how to do this?
4
votes
1answer
2k views

Why does my firewall (iptables) interfere in my bridge (brctl)?

I set up a bridge br0 "attached" to two interfaces: eth0, my physical interface connected to the real LAN, vnet0, a KVM virtual interface (connected to a Windows VM). And I have this single ...
3
votes
1answer
114 views

How to combine iptables rulesets

Say there are several iptables scripts (run at boot time), all of which run something like iptables -A ... to add rules. I'm thinking this could be improved, turning all those shell scripts into text ...
2
votes
0answers
72 views

Defining IPv6 chains in ip6tables-restore/iptables-restore files, is it possible?

The format for the files generated by iptables-save/ip6tables-save and loadable through iptables-restore/ip6tables-restore stipulates that one can prepend -4 or -6 respectively so as to maintain the ...
1
vote
1answer
1k views

iptables based redirect captive portal style

What is a iptables set of rules that will force hosts connected to a access point, that try to access any website (port 80 of any ip or hostname) to be redirected to another device on the network ...
4
votes
2answers
250 views

Can iptables rules manipulate IP sets?

In iptables-extensions(8) the set module is described and it is discussed that it is possible to react to the presence or absence of an IP or more generally a match against an IP set. However, it ...
2
votes
1answer
59 views

How can I let ipset entries “age”?

I am trying to establish a whitelist of clients that have successfully logged into the system, using ipset. What options do I have to let an entry age so that I can later discard it based on its age? ...
1
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0answers
33 views

How do I route traffic between eth0:0 and eth0 [duplicate]

I have been trying to convert my linux box which is running Mint into a router. eth0 has a public IP address of 71.xx.xx.xx. I created an eth0:0 and gave it an IP address of 10.0.0.100. I started a ...
0
votes
4answers
977 views

Converting Linux into a Router- Traffic from eth0:0 to eth0

So I have been trying to convert my linux box which is running Mint into an router. eth0 has a public address that has 71.xx.xx.xx for an IP addr. I created an eth0:0 and set it an IP address , ...
2
votes
1answer
77 views

Do I have to swap IP sets, or can I add/remove on the fly?

I was wondering about the semantics of ipset(8). Is it possible to add a rule matching a set to iptables and then manipulate the set, or can I only create a set and swap it for an older set in order ...
7
votes
1answer
828 views

delay to get password prompt when ssh'ing to a public server

i have a server (debian 7) setup in my university with public ip. when I ssh into the system (from outside the campus), I get a weird delay of 5-10 seconds before I get the password prompt. Why is ...
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0answers
220 views

iptables server behind NAT accessible from outside as well as inside the nat

I have 2 machines with a KVM running on each machine - so two kvms with the below networking Host 1: 192.168.10.100 (eth2) 10.10.100.1 (virbr1) KVM 1 (NAT with Host 1): 10.10.100.128 (eth0 ...
2
votes
2answers
136 views

Does IP tables need to be configured or is a stand alone firewall sufficient?

I have two desktops and a laptop running Arch Linux. I have not setup any iptable rules on any of the machines, and I am curious if I should. One desktop is only used in my home network and is ...
0
votes
0answers
169 views

What is wrong with these iptables' rules?

The following is what I got after googling: iptables -A INPUT -i lo -j ACCEPT iptables -A OUTPUT -o lo -j ACCEPT #allow loopback access iptables -A OUTPUT -d 255.255.255.255 -j ACCEPT #make sure you ...
4
votes
2answers
3k views

Why is the firewall off by default with Linux Mint?

One of the most common recommendations that I read for users that recently installed Linux Mint is to enable their firewall, which is pretty simple to do. But why is the firewall off by default in the ...
1
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0answers
103 views

Linux firewall distro that can configure a vpn connection as a WAN interface?

I'd like to setup linux as a router w/firewall between My machine and the internet. The linux box should connect to a VPN account using OpenVPN on boot (managed to get that done). Then the firewall ...
4
votes
1answer
1k views

bridge does not forwarding packets centos

I am using CentOS 6.5 64 and use xen to create a virtual machine (CentOS) ifconfig [root@CentOS ~]# ifconfig eth0 Link encap:Ethernet HWaddr 08:00:27:54:B3:FA inet6 addr: ...
1
vote
1answer
143 views

configure exim for system email forwarding (outside) , on a server with dynamic ip, behind a DNS router

Trying to configure exim to deleaver email to the outside world. I/We need to send email outside just for centralize certain admin notifications. Working on an already configured debian webserver, ...
4
votes
1answer
3k views

How to check if port forwarding is enabled?

I have just set up a DNS server for my own network, and many guides online suggest to make sure that port forwarding on port 53 is not enabled. The thing that is not clear to me is this: should I ...
1
vote
1answer
227 views

Does an in-kernel firewall sit between the network access layer and Internet layer?

This question is a follow-up to my previous question. Logic for me to says that an in-kernel firewall sits between the network access layer and the Internet layer, because it needs to have access to ...
0
votes
1answer
775 views

Socket Connection Refused (raspbian) but ports are open for connections

I'd like to establish a connection between my client and raspbian. Within my network, I can connect to my service at any time without any problems. Now I want to connect to my service via the ...
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0answers
141 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 ...
0
votes
1answer
78 views

iptables correctness verification

I have so many questions around iptables and how it works. But we're using a modified kernel, and hence whatever experiment I try and fail, I can't be sure if it happens with Linux in common or just ...
1
vote
1answer
773 views

Iptables rule to allow only one port and block others

We have two apps running (on top of linux) and both communicates through port 42605. I wanted to quickly verify if this is the only port that's been used for communication between them. I tried below ...
0
votes
1answer
83 views

What does the last column in this IP table mean?

From a tutorial, I run $sudo iptables -A INPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT $ sudo iptables -L and get target prot opt source destination ACCEPT ...
2
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0answers
516 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 ...
2
votes
1answer
467 views

Webserver establishing new outgoing connections from port 443

I've been trying to configure the firewall on a webserver running Apache using iptables commands. I took the approach of blocking all outgoing connections, except for those that are required. ...
2
votes
0answers
219 views

IPtables rule to double NAT [closed]

Let me rephrase it.. I just need an IPtable rule to do double NAT-ting.. Host A - Host B - Host C - Host D Host B should do both source NAT and destination NAT, so that my request from Host A ...
4
votes
1answer
269 views

How does iptables recognize packet state?

Consider these two sets of rules: Set A -A INPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT -A INPUT -j REJECT -A OUTPUT -j ACCEPT Set B -A INPUT -m conntrack --ctstate ...
1
vote
1answer
466 views

iptables forwarding between subnets

I want to forward traffic between two subnets, I'm not very familiar with iptables. The forwarding works except when iptables is enabled. There must be something wrong with the rules, though ...
4
votes
2answers
2k views

Can logging be enabled in FirewallD

I'm running Fedora 20 and would like to see what my firewall is doing in the background. Is it possible to view a log of the traffic blocked by FirewallD?