Signature for HULK attack?

Evan.Sink — Fri, 17 Mar 2017 20:22:46 GMT

Hi Everyone,

We are in the process of migrating from Cisco ASA firewalls on our Edge to PA 5020. Recently one of our websites was hit with a DDoS attack. After analysis, we determined that it was the HULK attack.

I got my hands on the HULK python script

https://packetstormsecurity.com/files/112856/HULK-Http-Unbearable-Load-King.html

and I'm currently testing it against a server behind my PAN. I have DoS Zon protection turned on and I verified that SYN floods and UDP floods are blocked like nobodies business, but when I run this script it takes the server down to it's knees and the PAN sees nothing wrong.

Can anyone help me figure out how to prevent this attack?

Re: Signature for HULK attack?

Evan.Sink — Mon, 20 Mar 2017 21:17:14 GMT

Hi Everyone!

After discussing with PAN Support we did come to a resolution on this.

The solution is to create a DoS protection policy (specifically the SYN Flood settings) and create it as a Classified Profile using RED. SYN Cookie is not an option against this attack because of the way HULK is written. Basically the Client establishes an absurd amount of legitimate sessions with the server, then does an equally absurd amount of bogus GET requests which eventually takes a server to it's knees.

The trick here is to determine how many SYN pps are typical for your enviornemnt, or the group of servers you want to apply this policy to. For me, I was seeing less than 10 SYNs per second from any given client so I set all the RED settings in the SYN flood protection to 25. This makes sure that a busy client still works fine, but anything that is abnormal gets dropped.

I tested the HULK attack again with this DoS Protection profile in place, and the server was protected.

If anyone has this same issue and has a question that I did not cover above please feel free to reach out.

thanks!

/Evan

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Signature for HULK attack?

Re: Signature for HULK attack?