Custom Signature for Email Headers

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Custom Signature for Email Headers

L3 Networker

I am trying  to create a custom signature with the purpose of preventing malicious/phishing/spam emails with the firewall before it hits our mail gateway. For the most part we have been successful with this technique but I am struggling with creating a signature to essentially work as a wildcard. If anyone could take a look at my scenario and provide any feedback it would be much appreciated. Below is my example:


Scenairo: we are receiveing unwanted emais from the following email address


As you can see the consistent parts of this type email campaign is the I am hoping to come up with a signature using email headers to wildcard the 'abc, abcd,abcda, etc'  as I dont want to be writing individual signatures for each sub domain as this could include upto 15 different representations of 'abc'.


I thought this would work scanner@(.*)(\.domain\.com) but does not appear to be the case.pic.PNGpic.PNGpic.PNG


L4 Transporter

Good afternoon!


I would try:




This operates under the assumption that the child domain under consists of any number of the characters a-z.

Thanks rcole. I will give this a shot.

Unfortunately this signature did not work either.

Hi clewis.


I tested this signature in a lab with every variant of the domain you provided, and it triggered in each instance.


Do you have a packet capture of the offending traffic?

I've been using this method for a while successfully...


I think I may be having an issue with decryption which may be casuing the issue. Just getting back around to looking at this one

  • 6 replies
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