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“Sexfavor” Email Scam Delivers Danabot

Sextortion has been a widely used theme in spam campaigns since Q1 of 2018. From simple crafted emails containing just plain text, extortion scams have evolved – even to the point of adding malicious attachments in Q1 of 2019. Since then, we’ve seen more and more attackers use sextortion spam emails as the arrival vector of their malware.

Now it seems the people behind Danabot, a notorious banking trojan, are trying out a different theme in their email campaigns – and quite the opposite of extortion. Instead of threats, the email body contains enticing text about sexual favors. The ruse goes like this: because of the sender’s unfavourable circumstances, they are asking for bitcoins as financial support in exchange for sexual videos and/or photographs. In addition, as referred to in paragraph 2 of the email body, the sender has attached “personal video clips” to lure the email recipient into clicking.

Seg_sextortion_emailsample
Figure 1: Trustwave SEG Console displaying the scam email leading to Danabot malware

 

THE ATTACHMENT

Attached to this email is a ZIP archive which contains a malicious VBScript file, which is a dropper hence the large file size (approximately 2MB).

Vbs_dropper
Figure 2: Source code snippet of the VB Script file “29769128629_82187.vbs” attached on the email sample shown in Figure 1

As shown in Figure 2, the file “29769128629_82187.vbs” contains obfuscated arrays where each will be de-obfuscated and written to disk as %temp%\tnTzi.txt. Then, the resulting file will be registered as a service. The written file %temp%\tnTzi.txt is the Danabot downloader DLL.

Process
Figure 3: Process tree from the dropper VBScript file “29769128629_82187.vbs” to Danabot DLLs

 

DANABOT

Danabot is a modularized banking trojan written in Delphi. It was first observed to be targeting Australian banks. Now, organizations in Europe are targeted as well.

Below are the new things we observed compared to our previous Danabot blog.

  • 10 hardcoded C&C IP addresses will be randomly connected to for Danabot modules and configurations files
    • BR - 45[.]168[.]210[.]12
    • CN - 121[.]23[.]160[.]107
    • CN - 211[.]95[.]57[.]124
    • DE - 89[.]144[.]25[.]243
    • US - 11[.]227[.]123[.]3
    • US - 66[.]63[.]159[.]193
    • US - 149[.]28[.]180[.]182
    • US - 161[.]11[.]65[.]218
    • __ - 228[.]114[.]253[.]168
    • __ - 230[.]47[.]242[.]100          
  • Target banks listed in the Web Configuration file includes banks from Germany and more from Australia.
    • Australia
      • BankSA
      • Bank of Melbourne
      • George Bank
      • CommBank
      • NAB
      • ANZ
      • Westpac
    • Germany
      • Sparda
      • Comdirect
      • Deutsch Bank
      • Berliner Bank
      • Norisbank
      • Targobank
  • Wildcarded URIs were also used to increase the number of targets in Germany
    • https://*.de/banking-/portal?
    • https://*.de/banking-*/portal;*
    • https://*.de/portal/portal*
    • https://*.de/privatkunden/*
    • https://*.de*abmelden*
    • https://*.de/de/home*
    • https://*.de/en/home*
    • https://*ptlweb/WebPortal

IOCs

File     SHA1
29769128629_82187.vbs f246c30c93de30257b103099d1aca3231dc4b200
%temp%\tnTzi.txt ff50b1db2ee97c5820b580503e7e7b70d95a393a
%programdata%\33C1F507\96B9B0C2.dll 4f0437b370e05d562f64ec1a4492ebeb560eecf8

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