Signature by hostname

[JuanB]

Hello guys,

We recently discover that sometimes, ramdonly, host called "Windows7" trays to mount a shared folder from our fileserver/DC. We discover this because our SIEM correlated some events from de DCserver. Sadly this SIEM do not show us the Source IP Address so,  we add a PAN  in SPAM port mode to the switch to tray to capture the ms-smb fail logons.

We started by adding the default custome signature and setting up to triggers with 5 events in 120 seconds (just like the SIEM's alert) but that do not work. Now we are traying to make a custome signatere that triggers when any package with the string "jbonaldo" goes through the PAN (jbonaldo is the host name).

I already read the "creating customg signature rev b" and I can not find any reference to SMB2 for the context field, so i try to use the "unknown-req-tcp-payload". I also tray setting up the string in clear text and/or hexadecimal.

BTW, I already create a vulnerability profile and append that to the security rule (just to be clear 🙂 )

what i am doing wrong?

[rcole]

Good afternoon.

For requests of this nature, please try to provide a packet capture if it is possible, highlighting the traffic you wish to create a signature on. It will greatly improve our ability to help you.

It sounds like you want to trigger off something specific in SMB traffic, though based on your post above I'm not 100% certain what the actual offending traffic is. Would you mind elaborating slightly?

As far as SMB based signatures go, we currently have one context for SMB, which is "ms-ds-smb-req-share-name" detailed on page 27 of the creating custom signatures document referenced in the sticky of this forum. 

Leveraging "unknown-req-tcp-payload" will not function as the traffic you reference will likely be caught by the SMB decoder. This would mean a custom signature is not possible with our current engine. "Unknown-req-tcp-payload" is for applications identified as "unknown-tcp" only, meaning we have no decoder for them.

[JuanB]

rcole, thanks for your answare. What im actually traying to do is capture in a pcap file every try of ntlm auth from a desktop machine with the hostname "jbonaldo". I attached you a pcap file with the capture and here it is a screenshot of what information im traying use to trigger my custom signature (and than, when the signature triggers capture this fail login).

In the pcap file (row 10) you can see that the hostname is actually in the package sended to the server so, in teory, we can see this information with the palo alto and trigger the custome signature and then, capture the traffic.

[rcole · Accepted solution]

Juan:

Thank you for the packet capture.

I can confirm that we currently do not have a context available in the custom signature engine for the SMB hostname. If this is something you'd like to have added, you should reach out to your account team representative and file a feature request for inclusion in a future version.

[JuanB]

OK, Cole thanks for your help.

BTW, do you know if there is any way to do what i need with the current PANOS?

THanks in advance.

[rcole]

Juan:

As far as I am aware, no. This is due to the fact that we don't have a context for SMB hostname publicly available to customers to write signatures on, and would require a feature request be filed.

[JuanB]

Ok, Again, thanks for your help.

[rcole]

Juan:

No problem, sir. Thank you for your patience and for providing the data you did.