How to bypass a Firewall Step By Step

That interface is conected to your network and get ip thru dhcp.

If you are able to connect a " whatever kind of evil device" to my private network, it is much easier to do anything for bypassing my security .... especialy if you connect a evdo device or modem router .... So ... where is the news?

I only connect to a widows pc that has 2 interface network. One for your network and the other for the netscreen device that will make the routed vpn. The windows pc will share the conection to your network to hide the netscreen device from your network. You never see my device you only will see your trust pc.

any ? regarding why we need a firewall ?

What would you like to tell us with this? If you have access to a windows pc and enough user rights to enable internet connection sharing, you could rather use some remote software like logmein or somthing ... From the firewalls point of view it´s also a well hidden data stream ... Or allow incomming connections on your modem .... That´s what many people misunderstand ... a firewall isn´t just a " godlike" device, that protects you from everything ... It´s a modular concept, containig of some hardware, rules for your users, policys, that they have to sign, before they sit on a PC. Limited access rights to significant data ... and so on. The point is: in all your scenarios, you must enter the office, connect some devices. That´s, what should be your problem! In a company that can´t trust it´s staff, a firewall is useless.

Yes. Everything is included in your last words. (In a company that can´t trust it´s staff, a firewall is useless. ) My other point it' s. A users with good understand in firewalls can make any network vulnerable using my diagram. I did my diagram to sell a device ( a NAC ) to perform authentication of who is connected. But there is no ( nac) that can stop my diagram. If one of my users try to put my network vulnerable i want to stop it.

Exactly. Your internal users are the inside robbers. How can you protect from them ? a funny user can make everybody on security staff a ridiculous. The fight is from inside to outside.

Homey, This doesn' t make any sense. How does a user get an external IP address on any device past the first firewall? Oh... Why did that happen? Oh... that' s not secure, you should fire your poor IT workers. Thanks, Matt P.S. By the way, I hope that any employer trusts any network admin with their company data. If that trust isn' t there, then the network admin should be fired.

How does a user get an external IP address on any device past the first firewall? Oh... Why did that happen? Easy Verify the diagram. all networks are vunerable to that scenario. The internal user will make a ssl vpn ( port https at least open) , then the user share this conncetion. The firewall netscreen device will use that vpn to make and ipsec vpn to another firewall. This netscreen firewall will have and untrust ip private on the same segment as the user pc. The netscreen firewall will have a real Public ip on its trust interface. Then the netscreen device will MIP or map ip from the trust to untrust. and wala. your internal network will have a public ip reachable from any where.

So you' re allowing access to establish an SSL-VPN source IP address of the LAN subnet, off the internal interface? Where is the hole? Stop access from inside to outside? This is very interesting to me, so I' d like to understand it. This is a good argument for a MAC detection device (like the Cisco ASA).

You are missing some steps in your firewall logic, think of a firewall as a gate in a jail. A jail still needs guards, cells, cameras and locks. Without going to so much detail I can think of two main scenarios. 1. protect the LAN from staff 2. protect the LAN from outsider The most obvious problem I SEE is that you are allowing staff or intruder to add devices on your network, well just stop it. Why does normal staff need administrator or power user rights to add network devices? Turn off ICS Implement SOE Do a security check on your staff and hopefully your head sysadmin or firewall engineer does not have a criminal conviction for fraud. If you are allowing strangers access to your office to add devices, I could... call the phone company to install a telephone line + adsl and just connect it to your network. Actually, it might be easier to just walk in and add a wireless device to the network. Nah why don’t I just walk in take the server? I am just pointing out the no firewall is a complete security solution