Tagged Questions

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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4
votes
2answers
370 views

How can I use one network port for VPN and the other for everything else?

My Linux machine has two network ports with two IP addresses. I want to use one port for my VPN and accounting, and the other port for other usages. How can I tell Linux not to allow any requests from ...
3
votes
1answer
444 views

Using rsync + cron to sync a machine behind a firewall with my dropbox

I have a machine (A) behind a firewall with no access to the Internet, on this machine I can NFS mount directories on another machine (B) which can access internet, and is accessible from Internet, ...
3
votes
2answers
623 views

How to listen to all ports (UDP and TCP) or make them all appear open in Debian

I got an external Debian server. The problem is that my university campus doesn't allow connections to go outside when the port is different than TCP port 22, 80, 443, or UDP port 123. I tested them ...
0
votes
1answer
2k views

How to really security a linux-mint-desktop?

I'm installing some security software in my mint9Gnome. I first went to Firestarter and looks like a pretty start. Now I'm going to OSSEC and want some good tools to search my logs too. Thinking ...
3
votes
2answers
749 views

Letting NFS through a FreeBSD PF firewall

I'm trying to configure my firewall (PF) on FreeBSD to let NFS traffic through. I know that NFS uses both TCP and UDP to connect to the client along with a bunch of daemons that use random port ...
4
votes
1answer
830 views

Force VPN using IPtables?

I want to force the use of VPN using iptables, therefore while VPN is disabled no outgoing traffic shall be allowed (except maybe some DHCP stuff...). Now i guess I could just block everything not ...
9
votes
1answer
7k 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 than whether should I select SNAT or Masquerade? Give me some ...
3
votes
2answers
475 views

Recommended reverse firewall applications for linux?

I'm looking for a reverse firewall, something like Little Snitch for Linux, but my google-fu is failing me. Does something like this exist on Linux?
3
votes
1answer
286 views

Converting a line from a firewall on OpenBSD 4.9 to OpenBSD 4.7

What is the OpenBSD 4.7 equivalent of this line from OpenBSD 4.9 for use with pf? no nat on egress proto udp from 192.168.1.10 port 4672 to any
0
votes
1answer
682 views

Can't connect remotely to server running redhat (ec2)

I created a RedHat 6.1 VM with EC2. Logged in as root, I installed (unzipped) JDK1.7 in /root/bin/jdk1.7.0 and installed (unzipped) GlassFish 3.1.1 in /root/bin/glassfish3. I set JAVA_HOME and ...
-1
votes
1answer
9k views

What is sport and dport?

I want to stop internet on my system using iptables so what should I do? iptables -A INPUT -p tcp --sport 80 -j DROP or iptables -A INPUT -p tcp --dport 80 -j DROP ?
2
votes
1answer
2k views

iptables rule to allow access to internet

I made default policy of my machine- iptables -A INPUT -j REJECT #DROP ALL PACKETS TO INPUT CHANNEL INPUT channel has been blocked. Now I want to allow only some specific services like I should be ...
5
votes
4answers
2k views

How can I send spoofed packets in Linux

In order to test a firewall, I want to send malformed packets to its interface, regardless of my routing table. Is there a way to ask linux "send this exact tcp package, to this MAC address, ...
2
votes
2answers
467 views

Security with Kernel IP Forwarding Enabled

I recently enabled IP Forwarding on a production web server that also acts as a VPN server. What, if any, security issues did I just set myself up for? And are there any iptables rules I should set ...
5
votes
4answers
10k views

Set some firewall ports to only accept local network connections?

Basic firewall question: How do I set up the firewall on a system in a LAN so that some ports are only open to connections from the local area network, and not from the outside world? For instance, ...
1
vote
1answer
1k views

Fedora firewall with UPnP?

I'm using Fedora 15 and Transmission BT client. Transmission can't open ports unless the firewall is disabled. I searched some posts that said add 1900 to the trusted ports, or via a iptable rule: ...
3
votes
1answer
291 views

Setting up the firewall for amule on OpenBSD 4.7 gateway

I'm trying to properly setup the firewall on my gateway (OpenBSD 4.7) using pf to allow amule (on 10.0.0.104) to operate properly as discussed here: Now I know pf has changed a bit from OpenBSD 4.7 ...
2
votes
1answer
3k views

How to stop firewall from writting logs to /var/log/messages?

I'm running OpenSUSE 11.4. The problem is that I can set easily what to log, but not where to log. And currently the same logs are written to /var/log/firewall and /var/log/messages. I still want ...
4
votes
2answers
2k views

What tools do I need to intercept and change an incoming packet on a WP2-Personal wifi hub

Which tools should I research into to intercept a plain text packet, edit it and then continue it on it's way. I am using Ubuntu 11.04 and Backtrack 5; my wifi is WPA2-person encrypted. I need to edit ...
4
votes
2answers
4k views

How to limit P2P/torrent traffic on an OpenWrt 10.03 router?

We have a WRT160NL router with OpenWRT 10.03, and a 60-70 Mbit connection (from ISP, don't ask why). This router can do 30-35 Mbit on ethernet(i mean cable)..ok! There are ~7 PC's using this Wireless ...
1
vote
1answer
543 views

Why does Firestarter say my firewall is active but ufw status shows it as inactive?

I am using Linux Mint and am having the following issue. Firestarter tells my that my firewall is active and it does indeed seem to be active. However when I type "sudo ufw status" into the terminal, ...
3
votes
1answer
207 views

iptables infographic

Is there an infographic somewhere that describes the logical flow of iptables? Specifically, I'm looking for something that diagrams which point in the process ip_conntrack applies.
0
votes
3answers
572 views

EBtales not working

I wanted to go a little bit further and install EBtables (the 2-layer filtering and routing table). The purpose of it was to only allow the minimal necessary(IPv4 and ARP). To test it I ran: ebtables ...
6
votes
4answers
7k views

Fail2ban block with IPtables doesn't work on Debian Lenny. [moved ssh port]

I've recently decided to do some security maintenance. I saw my logs, and there were some tries against my SSH server. At first, I moved away the SSH port from the default 22. After it, I read ...
1
vote
2answers
9k views

Problems setting up TigerVNC and firewall

I have a box running a fresh install of Fedora 15. I've installed TigerVNC server on it and client on my Windows machine. I've added -A INPUT -m state --state NET -m tcp -p tcp --dport 5900 -j ACCEPT ...
6
votes
2answers
681 views

Configuring a vncserver so it's only accessible from my ssh tunnel

Since I use vnc through an ssh tunnel, is there any way I can block the open vnc port that the remote machine is listening on without it affecting my ability to use the ssh tunnel? Both machines are ...
2
votes
3answers
395 views

Port monitoring on GNU/Linux based NAT router

I am using a Ubuntu machine as a NAT router. How can I find out the following: the ports on which the LAN machines are listening or communicating (both tcp and udp); which local machines have ...
2
votes
1answer
2k views

iptables/pf rule to only allow XY application/user?

I think there is no iptables/pf solution to only allow an XY application on e.g.: outbound tcp port 80, eth0. So if I have a userid: "500" then how could I block any other communications then the ...
1
vote
1answer
1k views

I can't figure out how to install Firestarter Fedora

I am feeling stupid. I have been searching for 3 hours with no success. I installed Fedora 14 and tried to do yum install firestarter but the package was not found. I also tried from a GUI and found ...
7
votes
1answer
563 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 ...
7
votes
2answers
14k views

iptables: allow certain ips and block all other connection

How do I allow certain ips and block all other connection in iptables?
2
votes
1answer
482 views

Is there any PF log parser for FreeBSD

I am runing FreeBSD 8 stable with PF as firewall, I am looking for any tool for parsing PF log's.
3
votes
1answer
174 views

Linux App that monitors log and add rules to iptables

I used to use a linux software that monitors logs like http, ssh, etc and if it detects that someone is trying to use brute force, it blocks that ip by adding a rule to iptables. I forgot what that ...
2
votes
1answer
587 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 ...
-1
votes
1answer
2k views

How to block HTTPS site using RHEL Squid?

I want to block HTTPS sites using Linux Squid server. How can I do this?
2
votes
4answers
543 views

What does this iptables command do?

Does iptables -I INPUT -j ACCEPT open all ports?
10
votes
3answers
4k views

Is there a way to find which iptables rule was responsible for dropping a packet?

I have a system that came with a firewall already in place. The firewall consists of over 1000 iptables rules. One of these rule is dropping packets I don't want dropped. (I know this because I did ...
3
votes
1answer
385 views

1000 iptables entries on CentOS?

I just got a new dedicated server with CentOS and I'm trying to debug some network problems. In doing so, I found over one thousand iptables entries. Is this the default on a CentOS system? Is there ...
1
vote
2answers
906 views

iptables rule for local network with free internet blocking unrequested connection from internet to server?

I have a home server (with slackware 13) with a eth0 for the local network and a eth1 for the internet (cable modem with dynamic ip). While I do want to learn more about iptables I am still on the ...
4
votes
3answers
342 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 ...
3
votes
3answers
277 views

Turning an old computer into a network firewall

I have an old Dell Dimension with two ethernet cards, and I need to turn it into a firewall. I've tried FireStarter and IPCop, but I don't think I'm setting them up right. Here's the setup that I'm ...
0
votes
2answers
140 views

Where to handle packets between clients?

"Server": 192.168.1.1 I want to "theoretically" disable that the clients can "ping" each other. Can i use an iptables rule for it? e.g.: iptables -A FORWARD -m iprange --src-range ...
1
vote
1answer
1k views

IPTABLES rule for separating users

I have an OpenWrt 10.03 router [ IP: 192.168.1.1 ], and it has a DHCP server pool: 192.168.1.0/24 - clients are using it through wireless/wired connection. Ok! Here's the catch: I need to separate ...
1
vote
2answers
671 views

squid (reverse proxy) configuration

I would like to configure squid in such way, so that only specific (public) ip (reverse proxy), could connect to the server, but I don't know how... can someone tell me how to do this?
6
votes
3answers
377 views

SpamAssassin Under Linux VPS

I am getting bald with this guys: On a Linux VPS (CentOS), I have setup a mail server (Exim+Dovecot+Clamav+SpamAssassin) but scanning mail for spam using SpamAssassin is proving to be a challenge. I ...
-1
votes
1answer
1k views

How can I open port 21 on a Linux VM?

I need to open port 21 on a Linux (CentOS 5) virtual machine I have. I have tried several Google solutions, but none are working. I was wondering if someone could tell me how to do this. Below is ...
1
vote
1answer
727 views

Could not connect to host 127.0.0.1: Connection refused

Could not connect to host 127.0.0.1: Connection refused. - I am getting this error message on ktorrent on slackware 13.1 and the torrents cannot start. I tried to reconfigure the ktorrent prefernces, ...
1
vote
1answer
496 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
4answers
4k views

Debian: Which firewall for a newbie?

I have to install a firewall on my server (so without X Server). It's a debian lenny. If it is possible, I want to avoid the use of iptables. Is there a way to install/configure a firewall for a ...
4
votes
3answers
679 views

tunneling VNC/rdesktop over ssh

I'm having a friend behind a firewall, with a windows computer. I'm having a Linux machine at home which is not behind a firewall. I want to have an rdesktop connection to his machine, without using ...