A Firewall is an application or hardware device used to inspect and filter network traffic.

learn more… | top users | synonyms

11
votes
8answers
28k views

Blocking Facebook and Myspace by IP address

I'm having some trouble making a Cisco ASA device block certain social networking sites which have become time sinks in our office. This question is really in two parts: Is there a reliable way to ...
15
votes
3answers
10k views

How to turn iptables stateless?

I'm running a Linux server that - from time to time - faces heavy load and the conntrack table overflows. Since it's iptables firewall ruleset is very simple I'd like to turn it to stateless mode. I ...
14
votes
3answers
1k views

Debugging iptables and common firewall pitfalls?

This is a proposed Canonical Question about understanding and debugging the software firewall on Linux systems. In response to EEAA's answer and @Shog's comment that we need a suitable canonical ...
13
votes
5answers
24k views

Disable Windows Server Network Locations

I'm not sure what exactly this feature is called. But in Windows Server 2008, it has the Vista Public/Private/Domain locations. This makes sense for laptops, and none at all for servers. My problem ...
8
votes
1answer
1k views

Block outgoing connections for certaing uids (root, apache, nobody)

With iptables in CentOS 5 and 6 Linux - how can you please prevent processes running as root, apache or nobody from initiating outgoing connections? On CentOS 5 Linux I've tried putting these lines ...
7
votes
2answers
12k views

Reduce firewall rules by half - one iptables rule for tcp and udp

I have a number of iptables rules on my firewall that look like this: iptables -A zone_lan_forward -p tcp -d 1.2.3.0/24 -j ACCEPT iptables -A zone_lan_forward -p udp -d 1.2.3.0/24 -j ACCEPT Is ...
2
votes
13answers
14k views

What free options are available for web content filtering? [closed]

I run the IT Dept at a small high school with about 500 users on the network. We have been using SurfControl for this which has been handy because it backs into MS ActiveDirectory very well. We ...
4
votes
3answers
8k views

How to configure remote access to multiple subnets behind a SonicWALL NSA 2400

I have a client that uses a SonicWALL NSA 2400 as their firewall. I need to setup a second LAN subnet for a handful of PC. Management has decided that there should be a second subnet even though ...
4
votes
3answers
4k views

Blocking IP behind a load balancer

Is there any way to block IP address of an intruder (or any IP), when our server is behind a Load balancer. For example if my servers are behind ELB (Amazon ELB) or Rackspace Load balancer, i am ...
3
votes
11answers
2k views

Which hardware for an entreprise router/firewall/content filter/proxy on a single server [closed]

I have to set up a "secure" network for my boss. For now, I have a ADSL router linked to a switch. All users are connected to this switch. Security is obviously bad. I want to put a server between the ...
3
votes
2answers
1k views

Open Source XML Firewalls? [closed]

Does anyone know of any open source XML firewalls that provide equivalent functionality to DataPower, Vordel, etc?
3
votes
1answer
1k views

UFW/IPTables: how to securely allow authenticated git access with github

This is how I setup my iptables with UFW: sudo ufw default deny incoming (deny all incoming) sudo ufw default deny outgoing (deny all outgoing) sudo ufw allow out 53 (accept outgoing DNS traffic, ...
3
votes
1answer
4k views

How can I rate limit SSH connections with iptables?

I'm trying to limit the number of possible SSH connections to my server but it just seems to lock me out every time. I'm not very familiar with iptables but I've been reading up on the rules that I ...
2
votes
1answer
19k views

How to configure PFSense firewall with external transparent Squid proxy?

I am using PFSense 2.0 and trying to get transparent proxy to work. As the internal Squid won't work with loadbalancing and dual-wan (and it seems Squid doesn't work at all on the latest build), I ...
2
votes
4answers
18k views

FTP/SSL in passive mode with portrange, which ports has to be open on the firewall?

We have to use FTP over SSL on our server and use a portrange with 5 ports for the data connection. A firewall is between client and server. We have to know what we have to open at the firewall: port, ...
2
votes
3answers
9k views

Ubuntu only allow incoming access from 192.168.0.0/8 or server IP address

How can I make it that only approved IP addresses have access to my Ubuntu server 12.04 I only just set it up.
2
votes
2answers
2k views

socat connect-connect “proxy” two inbound TCP connections to expose a firewalled service?

I'm struggling a bit trying to see how to use socat (or a similar TCP port redirector) to expose a firewalled service on a PC. Here's the scenario: I have a server PC which will be acting as a ...
2
votes
1answer
9k views

How to make iptables ALLOW rule for multicast?

I have two servers that uses ucarp as failover. On each server eth1:1 is reserved for ucarp's keepalive connection. ucarp uses the destination IP as multicast address 224.0.0.18. On ucarp master ...
2
votes
2answers
2k views

IPFire firewall under Hyper-V. How to get synthetic devices working?

The latest version of IPFire (v2.7 core 38) uses the linux 2.6.32.15 kernel. This includes Microsoft's Hyper-V synthetic drivers. How do I get them working? When IPFire boots, it loads the hv_vmbus ...
1
vote
4answers
4k views

Linux Firewall + Loadbalancer distribution

Can anyone recommend a Linux specialized distribution (or appliance) which provides both Firewall and Load-balancer? Something similar to IPCop for example, but containing LB as well? Thanks in ...
22
votes
1answer
24k views

What does “!Z” and “!X” mean in a traceroute?

When you see "!Z" or "!X" in a traceroute, what does that mean? Where is it coming from, and how do I fix it?
7
votes
3answers
14k views

Disabling Windows Server 2008 firewall

I applied a Windows firewall rule that blocks all tcp connection and thus kicked myself out of remote desktop on a dedicated server. I managed to get into recovery via VNC, which is basically a ...
5
votes
4answers
694 views

iptables: change policy or use catch-all rule?

What do you do when setting up iptables: change the default policy (iptables -P INPUT DROP, for example) or add a catch-all rule at the end of the ruleset (iptables -A INPUT DROP)? If you do prefer ...
5
votes
2answers
2k views

Linux fails to interpret ACK, keeps resending SYN+ACK

The following is a wireshark dump of the problem occurring, IP-adresses replaced with 'client' and 'server': 4414.229553 client -> server TCP 62464 > http [SYN] Seq=0 Win=65535 Len=0 MSS=1452 ...
4
votes
5answers
5k views

connect to ssh server thru 80 via HTTP proxy?

Please help: I want to connect to my ssh server at home However, I'm behind a corporate (CORP) firewall, which blocks almost all ports (443, 22, 23 etc). But it seems that 80 is not blocked, coz I ...
4
votes
3answers
8k views

How long does it take for an iptables rule to apply?

How long does it take for an iptables rule to apply? I use a script with the code below in an attempt to block hosts, but they don't appear to take immediately. Is there some delay, is iptables not ...
4
votes
5answers
1k views

Is it beneficial to chain multiple firewalls at the perimeter? [closed]

I'm currently running ISA 2004 and will soon be running an Untangle box. I've always felt a tiny bit safer putting these more advanced software firewalls behind a dumb hardware firewall (like mid-...
3
votes
3answers
13k views

Enabling http access on port 80 for centos 6.3 from console

Have a centos 6.3 box running on Parallels and I'm trying to open port 80 to be accesible from outside tried the gui solution from this post and it works, but I need to get it done from a script. ...
3
votes
3answers
17k views

Cisco ASA logs “regular translation creation failed for icmp …” for DNS traffic, yet it works

Every few minutes our Cisco ASA 5505 firewall is logging errors that I can't figure out with my limited Cisco experience. Severity Date Time Syslog ID Source IP Destination IP ...
3
votes
8answers
41k views

How to enable sshd on Fedora 11?

I have just installed Fedora 11 on my desktop system and would like to have sshd work. These are the steps I have done: Enabled sshd as a trusted service using system-config-firewall Restarted sshd ...
3
votes
1answer
2k views

iptables preroute localhost

I would like to forward all incoming traffic from a certain port to another one using iptables. The problem is that prerouting doesn't work for traffic from localhost. This topic suggests a solution: ...
3
votes
4answers
12k views

outbound ports that are always open

What are some ports that can NEVER be blocked outbound in firewalls, as doing so will stop basic internet use? Some I can think of are: port 53 udp/tcp -- dns, blocking this will prevent users ...
2
votes
2answers
843 views

Open VZ firewall solutions

Ive got VPS running on an Open VZ virtualisation instance. Unfortunately im having a lot of trouble getting a firewall up and running. Ive tried my usual UFW and shorewall, but neither of them would ...
2
votes
4answers
1k views

Linux router and firewall with IP accounting

I'm working on a project to replace my organisation's aging Slackware gateway/router/firewall machine, which will have several hundred users behind it. Previously we used rc.firewall but we are now ...
2
votes
2answers
2k views

UFW/IPTables: after setting default outgoing deny, and port 80 outgoing allow, curl still doesn't work

With UFW, I disabled all outgoing and ingoing traffic by default. However, I do allow port 80 in and out: sudo ufw default deny incoming (deny all incoming) sudo ufw default deny outgoing (deny all ...
2
votes
4answers
759 views

How to browse to a webserver which is reachable through the SSH port only

I have a server at work which is behind a firewall (the company's firewall) so it is reachable only thrugh port 22 (SSH). I'm able to connect to the server with putty without problems. Also, that ...
1
vote
1answer
2k views

CSF firewal - how does csf.allow work?

In my csf.allow file I have (something like): 98.765.43.21 tcp:in:d=20:s=12.345.67.89 tcp:in:d=21:s=12.345.67.89 Am I right in thinking that this will 1) always allow any service for 98.765.43.21 2)...
1
vote
3answers
2k views

iptables rule to block incoming/outgoing traffic to a Xen container

I'm trying to setup IPTABLES on my xen host server that will block incoming and/or outgoing access to a xen client on the same machine. Specifically, I need to block outgoing port 25 traffic and ...
1
vote
3answers
313 views

Network Question

I have a question about whether something is 'possible' by default or requires additional setup. Lets say I have two systems behind a firewall and they are in the same domain and subnet. System 1 has ...
1
vote
1answer
1k views

How to stop OpenEsb Glassfish Admin console from opening connection to glassfishesb.org

I have a Glassfish v2.1 app server (OpenEsb distribution) running behind a very restrictive firewall. Some times a bottom frame will appear, trying to connect to this address: http://glassfishesb.org/...
1
vote
2answers
5k views

pfsense setting up as transparent firewall - dhcp issue

I followed the directions to set up pfsense in bridged / transparent mode per the instructions at http://doc.pfsense.org/index.php/Configuring_pfSense However I can not get a dhcp address from my ...
0
votes
1answer
437 views

Can these IPv4 and IPv6 firewall rules be hardened any further? [closed]

I am running Ubuntu 10.04. Here are the IPv4 firewall rules that I've been using now for a few months: *filter #Allow all loopback (lo0) traffic and drop all traffic to 127/8 #that doesn't use lo0 -...
0
votes
1answer
1k views

How to relax firewall for UDP connections/ports for a specific IP address?

My server is Red Hat Enterprise Linux Server release 5. iptables version is v1.3.5. I want to allow all UDP connections / port for the IP address 192.168.0.200. This IP address is configured in my ...
0
votes
1answer
2k views

Multiple interface NAT routing

I have multiple internet connections from different ISPs and I need to route certain traffic over a particular ISP link. I am using Debian for this. The setup is as follows; eth0 (IP address is 192....
-1
votes
3answers
289 views

iptables — am I doing this right?

UPDATE Boy am I glad I asked. OK, I'll try again and post another question. I'd like to set up a CentOS 5.3 host to allow only ping, ssh, httpd, and SSL connections. After reading a tutorial and ...
-4
votes
2answers
2k views

iptables: open port 25 CentOS 7 [closed]

I have problems opening port 25 for sendmail on my CentOS 7 machine. Here's my iptables configuration: *filter :INPUT ACCEPT [0:0] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [0:0] -A INPUT -m state --...
7
votes
3answers
10k views

Why can't I ssh or ping my brand new Amazon EC2 instance?

I just created a free EC2 instance with all the defaults. It says it's running in the AWS Management Console. On the "Instance Actions" menu, I click "Connect". I copy the DNS name provided (looks ...
5
votes
9answers
4k views

Block users from Social networking websites while firewall is down

We currently have a SonicWall firewall, which does a pretty good job a blocking Social networking websites like Facebook and Bebo. The problem we are having is that sometimes we need to temporarily ...
4
votes
2answers
11k views

Windows Firewall 2008 Server - Allow only given IP in, block all others

I've got a Windows 2008 Server. It has the built-in windows firewall on it. I've played around with the Advanced settings where I can setup inbound/outbound rules, but it doesn't appear that I can ...
4
votes
3answers
2k views

Comparison of Firewall, Intrusion Prevention, Detection and Antivirus Technologies in Organizational Network Architecture

in these days i'm reading about intrusion prevention/detection systems.When reading i really confused in some points. First, the firewall and antivirus technologies are known terms for years, however ...