Comments on How To Test Your Linux-Distro Firewall

In some cases you could use Shields Up from grc.com to test your config, right?

--Supermike

Because grc.com is a joke. They were the "poster boy" that made Zone Alarm famous.

If you want to thoroughly test things, you don't go to some third party that promotes its own products. You use proven open-source tools from developers that have no money motivated motive. (As in they do it, because they love what they do).

Honestly, how can you trust grc.com if they don't reveal the details of their tests? (source code?). How do you know such online security tests are trustworthy?

Steve Gibson has nothing to do with Zone Labs.  They are currently owned by checkpoint.  He wrote that app as service to the security community to test the very first personal firewalls.  Which is the same reason he give people access to RSA random text generator to get true randome passwords (https://www.grc.com/passwords.htm).

 He also does a security podcast with Leo Laporte to promote computer security.  Listen to the podcast, you will find "they love what they do".  (https://www.grc.com/securitynow)

 None of this has anything to do with ZoneAlarm.

Uncue 

Grc.com is a great tool and serves it's purpose well.  Not everyone is a technical expert or wants to be in order to use their PC for the actual task at hand.

If you chose not to trust its tests/advice then you could equally doubt the validity of tests/advise on other sites - such as this one!

Grc.com has earned its trust over the years from the user/IT community.

PS.  Why doesn't Ubuntu (and many other Linux flavours) pass the port tests (they should be in stealth mode) out of the box?

Wrong. Steve Gibson is nothing but a fraud. You should do some research : http://allthatiswrong.wordpress.com/2009/10/11/steve-gibson-is-a-fraud/ Says it all. And it's true. Also cites resources and specific things he's said and done that show even more. WRT why Linux is not stealth. Keep in mind linux is often used for servers. Also keep in mind that you should not just drop all packets (say icmp). If you aren't a server or router, well ok. But fact is ICMP has its uses (error codes!); some isp's may even use it when you're having connectivity issues. But if you think all linux machines should be in stealth, then... maybe you should just not use email, web or anything else. What should be done (and is, last I recall of the distros I use or have used) is that services should not be running if not required; I know for sure I had to enable internet services in order for them to be up. And if you do enable firewall, although the rules are not the best method (eg it should be default policy set to DROP and only allow certain things) it still will not allow incoming connections unless you allow them (because of a reject rule). Fact of networks is, in order to provide services, the server need ports open. Linux does not need to be stealth but if it's a requirement for you, well it's not really hard to do, say : /sbin/iptables -I INPUT -j DROP (or set it's policy to drop or install a nat router with no forwarding ports or .. and so on) is it ? Firewalls are not designed to block everything in every situation. I hope you realize this. The fact the protocols have flaws is besides the point (and there are certainly workarounds - be it through syncookies, ignoring forwarding if not a router, limiting how fast packets can come in, and so on). (Yes, I realize the post is fairly old; however, it is a disservice to not make aware the fact that Gibson IS a fraud). Regardless, no computer is 100% secure anyway. Block all incoming traffic? Ok, who has physical access ? "I am the only one with a key to it" - that's security through obscurity because that does not mean no one can access it at some point. And physical access = root access (even with bios password you can always reset cmos, for one example).

would recommend to test with nessus also, http://www.nessus.org/
it can also find known security exploits in your firewall

For those who need good external scan test HackerTarget.com have nmap (trusted open source port scan program) free.

Payu