Tag Archives: firewall

Bypass stateful firewall on a Sophos XG

Usually, bypassing a firewall is not the best idea. But sometimes you have to. One case, where you want to bypass a firewall, is asymmetric routing.

MichaelGaida/ pixabay.com/ Creative Commons CC0

What is asymmetric routing? Imagine a scenario with two routers on the same network. One router offeres access to the internet, the other router provides access to other sites with site-2-site VPN tunnels.

Asymmetric Routing

Host 1 uses R1 as default gateway. R1 has static routes configured to the networks reachable over the VPN, or it has learned them dynamically using a routing protocol from R2. A packet from host 1 arrives at R1, is routed to R2, and is sent over the VPN tunnel. The answer to this packet arrives at R2, and is sent directly to host 1, because host 1 is the destination. This works because R2 and host 1 are on the same network. This is asymmetric routing, because request and answer go different ways.

In case of routing, this is not a problem. But if R1 is a firewall, this firewall might be stubborn, because it does not see the whole traffic.

Bypass the stateful firewall

I recently had such a setup due to some technical debts. The firewall dropped that “Invalid Traffic”. Fortunately, there is a way to bypass the statefull firewall. You can create advanced firewall rules using the CLI. There is no way to create these rules using the GUI. And this only applies to the Sophos XG (former Cyberoam products).

Login to the device console and select option 4. Then enter on the console the following commands, one per destination:

Make sure that you have a static or dynamically learned route to the networks. This is not a routing entry, it only tells the firewall what traffic should bypass the stateful firewall.

Secure your Azure deployment with Palo Alto VM-Series for Azure

When I talk to customers and colleagues about cloud offerings, most of them are still concerned about the cloud, and especially about the security of public cloud offerings. One of the most mentioned concerns is based on the belief, that each and every cloud-based VM is publicly reachable over the internet. This can be so, but it does not have to. It relies on your design. Maybe that is only a problem in germany. German privacy policies are the reason for the two german Azure datacenters. They are run by Deutsche Telekom, not by Microsoft.

Azure Virtual Networks

An Azure Virtual Network (VNet) is a network inside the public Azure cloud. It is isolated from the underlying infrastructure and it is dedicated to you. This allows you to fully control IP addressing, DNS, security policies and routing between subnets. Virtual Networks can include multiple subnets to reflect different security zones and/ or multi-tier designs.  If you want to connect two or more VNets in the same region, you have to use VNet peering. Microsoft offers an excellent documentation about Virtual Networks. Because routing is managed by the Azure infrastructure, you will need to set user-defined routes to push traffic through a firewall or load-balancing appliance.

Who is Palo Alto Networks?

Palo Alto Networks was founded by Nir Zuk in 2005. Nir Zuk is the founder and CTO of Palo Alto Networks. He is still leading the development. Nil Zuk is a former employee of CheckPoint and NetScreen (was acquired by Juniper Networks). His motivation to develop his vision of a Next Generation Firewall (NGF) was the fact, that firewalls were unable to look into traffic streams. We all know this: You want that your employees can use Google, but you don’t want them to access Facebook. Designing polices for this can be a real PITA. You can solve this with a proxy server, but a proxy has other disadvantages.

Gartner has identified Palo Alto Networks as a leader in the enterprise firewall since 2011.

I was able to get my hands on some Palo Alto firewalls and I think I understand why Palo Alto Networks is noticed as a leader.

VM-Series for Microsoft Azure

Sometimes you have to separate networks. No big deal when your servers are located in your datacenter, even if they are virtualized. But what if the servers are located in a VNet on Azure? As already mentioned, you can create different subnets in an Azure VNet to create a multi-tier or multi-subnet environment. Because routing is managed by the underlying Azure infrastructure, you have to use Network Security Groups (NSG) to manage traffic. A NSG contains rules to allow or deny network traffic to VMs in a VNet. Unfortunately a NSGs can only act on layer 4. If you need something that can act on layer 7, you need something different. Now comes the Palo Alto Networks VM-Series for Microsoft Azure into play.

The VM-Series for Microsoft Azure can directly deployed from the Azure Marketplace. Palo Alto Networks also offers ARM templates on GitHub.

Palo Alto Networks aims four main use-cases:

  • Hybrid Cloud
  • Segmentation Gateway Compliance
  • Internet Gateway

The hybrid cloud use-case is interesting if you want to extend your datacenter to Azure. For example, if you move development workloads to Azure. Instead of using Azures native VPN connection capabilities, you can use the VM-Series Palo Alto Networks NGF as IPSec gateway.

If you are running different workloads on Azure, and you need inter-subnet communication between them, you can use the VM-Series as a firewall between the subnets. This allows you to manage traffic more efficiently, and it provides more security compared to the Azure NSGs.

If you are running production workloads on Azure, e.g. a RDS farm, you can use the VM-Series to secure the internet access from that RDS farm. Due to integration in directory services, like Microsoft Active Directory or plain LDAP, user-based policies allow the management of traffic based on the user identity.

There is a fourth use-case: Palo Alto Networks GlobalProtect. With GlobalProtect, the capabilities of the NGF are extended to remote users and devices. Traffic is tunneled to the NGF, and users and devices will be protected from threats. User- and application-based policies can be enforced, regardless where the user and the device is located: On-premises, in a remote location or in the cloud.

Palo Alto Networks offers two ways to purchase the VM-Series for Microsoft Azure:

  • Consumption-based licensing
  • Bring your own license (BYOL)

The consumption-based licensing is only available for the VM-300. The smaller VM-100, as well as the bigger VM-500 and VM-700, are only available via BYOL. It’s a good idea to offer a mid-sized model with a consumption-based license. If the VM-300 is too big (with consumption-based licensing), you can purchase a permanent license for a VM-100. If you need more performance, purchasing your own license might be the better way. You can start with a VM-300 and then rightsize the model and license.

All models can handle a throughput of 1 Gb/s, but they differ in the number of sessions. VM-100 and 300 use D3_v2, the VM-500 and VM-700 use D3_v2 instances.

Just play with it

Just create some Azure VM instance and deploy a VM-300 from the marketplace. Play with it. It’s awesome!

Sophos UTM Home Edition license expired

Sophos offers a free license of their UTM firewall for private use. The product was originally developed by Astaro and since these days I use it at home. After the merger with Sophos I switched to the new Sophos UTM 9, still using my old license. I use it to seperate my test VLAN from my normal VLAN, and I use it as proxy with antivirus scanning for all my devices (iPhone, iPad, laptop etc.), but the UTM can do a lot more than this. This morning I wanted to read my Twitter timeline on my iPhone but I got no connection over WLAN. After disabling the proxy it worked fine. I took a look at the admin interface of my UTM and what did I see? An expired license. WTF?!


So I needed a new license file. I couldn’t imagine, that Sophos canceled all the feature for home uses. I went to the Sophos homepage, but I hadn’t a login for MyUTM. So I decied to register for a new UTM download to get credentials for the MyUTM website. After a short time I got an e-mail with the desired credentials. I logged in and downloaded the new license file.


After the installation of the new license file, everything was fine again.


As you notice, the new license has an expiration date. So better schedule an alarm to get a new one, before you miss your family IT SLAs. Nothing is worse than to have wife and kids complaining about not working IT services at home. ;)