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There is a new flavor of protocol reflection attacks on the streets!  

The TCP Middlebox reflection attack is the first reflection attack to utilize the TCP protocol. Traditionally the TCP protocol was not susceptible to spoofed source packets because of its state based nature (three way handshake).  Researchers at University of Maryland and the University of Colorado discovered that many network devices, such as load balancers, proxies, and firewalls, could be susceptible to specifically-crafted packets that could generate amplified traffic (up to 65x) at a victim.  These devices could be inherently susceptible to the spoofing because many of these devices have to contend with Asynchronous network traffic and out of order packets.


Akamai did a really great write up on what they saw and how they mitigated the attack. https://www.akamai.com/blog/security/tcp-middlebox-reflection


Shadow Server also has a write up. https://www.shadowserver.org/news/over-18-8-million-ips-vulnerable-to-middlebox-tcp-reflection-ddos-attacks/

So on to your firewalls:

The out of the box Palo Alto Firewalls do not appear to have any mitigation configured by default to protect against this attack.  But its not the end of the world.  Palo Alto and many other security vendors have low level TCP protection that basically normalizes TCP traffic and cuts out the flood attacks, malformed protocol attacks, etc., before they are even processed by your firewall. This minimizes  impact on the device resources like CPU and memory for these types of attacks.


In the Palo Alto world this is called "Zone Protection Profiles". If you run BPA (Best Practice Assessment) - which you should - then the Zone Protection Profiles are often flagged if you don't have them configured. 


The zone protection profile is pretty strait-forward to set up but, before you start, you need to do a little research and investigation into your device

  1. You need to determine the maximum CPS or connections per second your device can handle. This is a list of devices and their specs on the Palo Alto Networks site. https://www.paloaltonetworks.com/products/product-selection
  2. Next you will want capture some metrics around how many CPS your devices are seeing. https://docs.paloaltonetworks.com/pan-os/9-0/pan-os-admin/zone-protection-and-dos-protection/zone-defense/take-baseline-cps-measurements-for-setting-flood-thresholds/how-to-measure-cps
  3. Next you will want to do a few calculations and configure your zone protection profile. https://docs.paloaltonetworks.com/pan-os/9-0/pan-os-admin/zone-protection-and-dos-protection/zone-defense/zone-protection-profiles


Here is the "Cool SH*T Props" to Palo Alto Networks...when you create a zone protection profile, by default under the Packet Based Protection > and > 'TCP Drop the TCP SYN with Data' and 'TCP SYN ACK with Data' are already checked. This means when you apply your newly configured zone protection profile to your security zone it will protect you from current Middlebox vulnerability by dropping any of the cleverly crafted SYN packets because they would be larger then 0 bytes.



So I wanted to post a little bonus. Here is a quick and easy flood protection calculator I threw together in google sheets, just add your average CPS.