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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2
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1answer
967 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
569 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 ...
6
votes
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 ...
1
vote
1answer
857 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 ...
12
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3answers
42k views

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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0answers
9 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: ...
4
votes
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 ...
2
votes
1answer
94 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 ...
0
votes
1answer
24 views

iptables connection mark not balance

The following is my network topology: + + | | | | | | | ...
0
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1answer
92 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. ...
2
votes
1answer
380 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 ...
1
vote
1answer
93 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
votes
1answer
959 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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0answers
25 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 ...
0
votes
1answer
22 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
42 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 ...
0
votes
1answer
40 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 ...
3
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3answers
58 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 ...
0
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2answers
49 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 ...
4
votes
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 ...
3
votes
1answer
61 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 ...
0
votes
2answers
44 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 ...
0
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0answers
12 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 ...
2
votes
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 ...
0
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3answers
40 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 ...
0
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2answers
1k 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 ...
1
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1answer
148 views

ufw allow ssh - and then connection gets lost

I'm trying to set up a debian server in the cloud, over SSH. I log in using a key. After the initial startup I want to set UFW: apt-get install ufw ufw allow ssh ufw enable This is how I've done ...
3
votes
1answer
18 views

What does the “Incoming” option refer to in ufw?

I am configuring a firewall on my Linux Mint 17.2 to maximize security, mainly to put my mind at rest that no one will be able to do anything malicious. In gufw, there are options for allowing or ...
6
votes
1answer
39 views

connlimit counters start over after iptables restored

I have a connlimit rule in iptables that allow only 5 connection to port 80. iptables -A FORWARD -p tcp -m tcp --syn --dport 80 -m connlimit --connlimit-above 5 --connlimit-saddr -j DROP This ...
2
votes
2answers
4k 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 ...
6
votes
4answers
19k views

What prevents a machine from responding to pings?

I have a CentOS release 5.4 linux box on Amazon EC2 that I'm trying to set up to be monitored via Nagios. The machine is in the same security group as the nagios server, but it seems to be ...
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0answers
29 views

How to firewall qemu/kvm guest in host machine?

I have a qemu guest with following network topology: Internet <-> eth1.96[bridge]tap96 <-> eth0[guest] I need to allow access to guest machine only from one specific /24 network and I ...
4
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1answer
484 views

Block outgoing connections to certain IP using PF

Can someone give me a hint on how to setup a basic deny rule whenever any TCP request is sent to a specific IP address? I am using the PF packet filter. Any help?
1
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1answer
53 views

Iptables rules doesn't work as expected

I need to block access to my server from the outside of my private network. I need to allow pings from my server out only to my private network and answer pings initiated from my private network as ...
1
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0answers
50 views

How to block access to “private” host-only network from VirtualBox nat interface (separate host-only networks)?

Scenario: 1 VirtualBox host with many vms. Different host-only networks are configured for different vm categories: Some vms are "private", others are "standard" vms. Most of these vms, including some ...
11
votes
1answer
8k 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" ...
2
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2answers
2k views

tun0+ iptables rule

I'm trying to figure out what that + sign means in a rule such as this: -A FORWARD -i tun0+ -j ACCEPT I'm pretty positive it relates to vpn. I noticed a /dev/net/tun interface and a tun0 in ...
0
votes
1answer
56 views

Block incoming ssh with a reply message

I want to block all the incoming ssh to my system from a particular set of ips and send them a typical message saying something of sort: You don't have permissions to access this server as the ...
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0answers
13 views

Adding IP Blocklists to OSSEC

I've been reading through some documentations for OSSEC trying to learn some new tricks and such to make it more effective, and what I got really interested was looking into was seeing if it's ...
3
votes
1answer
138 views

Debian-Jessie: How do you check iptables status?

In old sysvinit I would just do service iptables status and see if it was running or not. But in newer Debian-Jessie I grep for iptables in the list of services and don't see iptables listed ...
14
votes
3answers
25k views

How can I block a range of IP addresses with an Amazon EC2 instance?

I know a certain range of IP addresses are causing problem with my server, 172.64.*.* what is the best way to block access to my Amazon EC2 instance? Is there a way to do this using security groups or ...
1
vote
3answers
80 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 ...
8
votes
3answers
20k views

IPTables - Port to another ip & port (from the inside)

I currently have a NAS box running under port 80. To access the NAS from the outside, I mapped the port 8080 to port 80 on the NAS as follow: iptables -t nat -A PREROUTING -p tcp --dport 8080 -j DNAT ...
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0answers
448 views

iptables: can't open tcp port

I'm running a Raspberry PI B+: Linux pi 3.12.28+ #709 PREEMPT Mon Sep 8 15:28:00 BST 2014 armv6l GNU/Linux The Raspberry is connect via lan (dhcp. ip: 192.168.78.29) to the local network. I'm trying ...
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0answers
49 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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2answers
99 views

Traffic of specific program through vpn [duplicate]

is it possible to only let the traffic of Deluge through a VPN (OpenVPN) and the other traffic not with iptables? Kind regards
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2answers
16k views

Difference between SNAT and Masquerade

I am confused what's the actual difference between SNAT and Masquerade? If I want to share my internet connection on local network then whether should I select SNAT or Masquerade?
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0answers
111 views

Is there a local “firewall” to block by “X-Forwarded-For” IPs behind the reverse proxies?

The situation is quite typical. I'm using CentOS + Apache(s) behind a Load-balancer for the WebSites. At this point, let's assume i don't have any access to the Load-balancer (or) let's forget ...
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0answers
42 views

How to limit the number of connections per-host passing through a router/bridge?

For some reasons, our Internet provider has a limitation on the number of simultaneous opened connections between the machines hosted in our private network and the Internet which is around 4000 ...
1
vote
1answer
630 views

PPTP Through IPTables

If this has already been answered, I apologize, I could not find an answer to this during my searching. I am new at Linux/Unix and I have recently implemented a Raspberry Pi firewall/gateway on my ...