[alienlove]

@SerpentFly wrote:

If every firewall were written as NetFirewall is, it would be possible to create a trojan horse using Winpcap and there would be no way to stop it.

Well, NeT Firewall is created to protect system from the external intrusion, not from the internal one. And trust me, it is not great problem to create a trojan which will bypass any firewall available on the market (such trojan still can be detected by analyzing infected system’s network traffic from another system). It requires strong skills in kernel development and not fast and easy to implement but still… It is 5 minutes to rebuild NeT Firewall to intercept winpcap, but it does not really makes sense. If you want to avoid installing trojan protocol just don’t work under admin account (without having admin rights non of the trojans can install a driver). In general don’t expect that if you install a firewall you can do anything and you are safe.

There is a separate set of products, so called kernel IDS targetted to protect your system from trojan software and system exploits. Firewall primary target is protecting your local network stack from external attacks and thats it. Implementing partial kernel IDS in the firewalls (like ZoneAlarm, an example) give you rather illusion of safety than real safety.

Hi!
As usual, thanks for your quick answer! 😀 Actually the online support for your prodouct is very quick 🙂
Don’t worry, this is the last time I bag you 😀
Actually, I think it’s very interesting and useful that NetFirewall runs on driver level. Just -in my opinion 🙂 – it would be nice for your firewall a bigger target, implementing some more functionalities.

Thanks a lot for your continuous attention,
Andrea

[alienlove]

@SerpentFly wrote:

NeT Firewall puts its packet filter between TCP/IP protocol driver and network interfaces. Winpcap installs its own protocol driver which works at the same level as TCP/IP (in parallel) and not intercepted by NeT Firewall. Basically, if you expect high security you should avoid having any other protocls (like winpcap) installed on the system. Primary purpose of NeT Firewall is protecting TCP/IP stack (not winpcap or any other custom protocol).

In general it is possible to intercept other protocols (like winpcap, ndisuio and etc..) in addition to TCP/IP protocol however this approach has some serious disadvantages (may break third-party NDIS intermediate drivers functionality, custom protocols and etc.) and since NeT Firewall is oriented on users who know what happens on their systems it is implemented on the current way.

Hi!
thanks for your fast answer 😀
We’re bugging you only because we’re testing your software here at our university department…
If it were possible to know what really happens on a network, maybe firewalls would not have a reason to exist. If every firewall were written as NetFirewall is, it would be possible to create a trojan horse using Winpcap and there would be no way to stop it.

Thanks a lot for your attention
Andrea

[alienlove]

@SerpentFly wrote:

With the FW on 3rd level security if I permit 21/TCP out and I block all the other outgoing traffic passive ftp doesn’t work.

FTP active mode uses two TCP sessions, one on server port 21 is a control channel and another data channel on server port 20. Control channel is established by client and data channel is established by server as a response on PORT command.

In passive mode both control and data channels are established by client. Data channel uses arbitrary ports >1024 on both server and client sides. In you case blocking all outgoig connections except port 21 does not allow client to establish data channel and FTP in passive mode does not work.

Dear SerpentFly
first of all I excuse for I’m late on answering you, I was busy with university: my porfessor Federico Simonetti of University of Milan says hello to you 🙂
What I’d like to ask you is: is there any way to make NetFW look at the PORT command in the control connection on 21 TCP port to automatically open the port the server wants to use to transfer data? As an example, Netfilter/IpTables can do it, and other commercial firewalls as well.

Thank you so much for your attention
Andrea

[alienlove]

@SerpentFly wrote:

The new version of NeT Firewall 2.3.2.3 has been released. We have updated the interpretation of IN/OUT keywords for TCP protocol, now it is applied to incoming/ougoing connections instead of incoming/outgoing packets. For other protocols IN/OUT interpretation remains the same. This should help to avoid missunderstandings in the future.

Thank you for your answers

I tryed this new version (2.3.2.3) and now the connection tracking on udp communications (DNS) works too 😉 .

there’s still the problem about the passive ftp . 🙁

With the FW on 3rd level security if I permit 21/TCP out and I block all the other outgoing traffic passive ftp doesn’t work.

How can I solve this problem?

Thanks a lot for your attenction

Andrea

[alienlove]

@SerpentFly wrote:

Well, you are right, but this is not about statefull inspection but the way the rules were originally implemented. IN means incoming packets, OUT means outgoing packets (in current implementation specifying only IN or only OUT for TCP protocol is senseless) and it is not exactly the same as IPFW rules where IN means incoming connection, OUT means outgoing connection for TCP. I agree that this may confuse a bit and probably it makes sense to change this behavoiur in order to avoid missunderstandings. Thanks for pointing this.

The rule you have created allows any system connect your port (from any port) 80 and connecting any your local port from port 80 what really breaks any security. Basically if you want to allow any kind of outgoing connections you are supposed to use on the the Stealth Security levels and create rules to drop undesired outgoing connections and may be some rules to open local ports if you also work as server. High Securty level was designed for servers which are supposed not to go outside world but just open some local ports to provide services for their users.

Dear SerpentFly, first of all thanks for your answer 🙂
Actually I think we just had a misunderstanding.
Our goal is to let only everything I want go out (e.g. HTTP and DNS just to browse over the Internet) and let go in only the answers from the servers I opened a connection to, just as statefull firewalling has to work. I know that DNS works on UDP and actually UDP doesn’t provide any type of connection (so talking about the state of connection on a udp comunication is not properly correct) but other statefull firewalls I have tried provide some kind of support for udp sessions (e.g. the connection tracking module of Netfilter/Iptables).
After reading your answer we did as you suggested: we put the FW on 3rd level security and just added the rules for HTTP and DNS, as in the images below.

HTTP works as expected, but DNS doesn’t, and in the log it’s reported the outgoing packets are processed by our own rules, but the answers by the “general security”: ingoing http is allowed as expected, but dns (we need to browse) is blocked by general security.

Do you have any ideas about it? Maybe it’s because NetFirewall doesn’t provide any support for connection tracking on udp communications?

Obviously we cannot add a rule allowing every ip address to contact me on my 53 udp port, even thougth in this way I can browse: that would be a huge hole in my security walls! A scan using nmap with 53 udp port as the source port would be allowed 😯

(if I permit 21/TCP out and I block all the other outgoing traffic passive ftp doesn’t works)

Have you any ideas about it?

Thanks a lot for your attenction

Andrea

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