Do I need a firewall if I use Linux?

I`m a home user, using Ubuntu 5.10. Do I need a firewall? Why Ubuntu does not have a firewall?

 

All OSs need protecting from hackers and the like, and Linux is no exception. That said, Linux is pretty secure "out of the box". The kernel already has packet filtering functions built in, such as IPTables, so a separate firewall isn't necessary if you have the built in filters set up properly. I'm not familiar with Ubuntu, but it may already be locked down with a decent default set of firewall rules such that an additional firewall is unnecessary. It also depends on which services your Linux is running and makes available over the net, such as telnet, HTTP and the like. Disabling unnecessary services and locking down services which are required is as important to secure Linux as it is for any other OS.

 

you have a firewall running unless you have disabled it - IPTables.

there are no services you need to protect by adding to IPTables, although you could install firestarter

sudo apt-get install firestarter

then go System>Preferences>Sessions>Startup Programs>Add

Startup Command - gksudo firestarter

Order - 50

http://img132.imageshack.us/img132/8626/screenshot6fz.png

when you have put it into startup you will be asked for your sudo password at boot to start firstarter. you won't notice it running though so you can open it and go to

Edit>Preferences>Interface then tick the box which says Minimise to tray...

http://img81.imageshack.us/img81/8566/screenshotpreferences9ep.png

i also have these settings enabled -

Enable ICMP Filtering, then enable these settings
ICMP Filtering - Echo Reply (pong) & Unreachable

http://img153.imageshack.us/img153/788/screenshotpreferences16lh.png

if you want to ping or do a traceroute then enable Echo Request and Traceroute just remember to disable them afterward.

here are some commands you might need

this one tells you the status - if it's running
sudo /etc/firestarter/firestarter.sh status

these next two start and stop it
sudo /etc/firestarter/firestarter.sh start

sudo /etc/firestarter/firestarter.sh stop

 

Yes, as Trickyricky indicated, Linux does have a firewall built right into the kernel, and it's a rather good one at that. It's called netfilter and the userspace module is iptables. It allows stateful packet inspection and is normally enabled by default in all modern linux distro's.

From the commandline, running:

Code:

lsmod |grep ip

should tell you if the iptables modules are loaded and if iptables is running.

BTW, most consumer hardware firewall routers (like those from netgear etc) just contain an embedded version of linux running exactly this.

Ned