Fake Office 365 Update Malspam Delivers Cthonic Banking Trojan

Trojan

The next in the never ending series of malware laden emails is an email with the subject of Office 365 pretending to come from Microsoft Security Team but actually coming via what looks like a compromised email account.

They use email addresses and subjects that will entice, persuade, scare or shock a recipient to read the email and open the attachment.

Microsoft has not been hacked or had their email or other servers compromised. They are not sending the emails to you. They are just innocent victims in exactly the same way as every recipient of these emails.

For some reason these emails are arriving in Outlook malformed with the attachment stripped. It might be something to do with the way my mail server delivers these or it might be the way the email is coded by the criminals sending these. It is highly likely that some recipients will receive a fully working copy.

Update: after digging around the mail server quarantine, I have found several of these, coming via numerous different compromised email accounts. All of them have the same malformed content with no accessible attachment.

office_security_update.zip : Extracts to: ms_office_update.exe Current Virus total detections: Payload Security |

One of the emails looks like:

From: Microsoft Security Team <acoruh@porland.com.tr>

Date: Thu 01/09/2021 19:22

Subject: Office 365

Attachment: office_security_update.zip

Body Content:

Good afternoon! It is Microsoft Office 365. Our specialists from the information security department found the possibility of infecting computers using documents created with Microsoft Office 365. We have updated the code for our products, but security update is in the attached file.

Copyright, All rights reserved. Office 365 and/or Microsoft, 2021.

Screenshot:

Email Headers:

IP Hostname City Region Country Organisation
212.174.1.100 mail.porland.com.tr Zeytinburnu Istanbul TR AS9121 Turk Telekomunikasyon Anonim Sirketi
127.0.0.1 Local IP
216.238.251.67 s67-251-238-216.dvec.az.wi-power.com Deming New Mexico US AS13904 Cherryland Services Inc

Received: from mail.porland.com.tr ([212.174.1.100]:38602)
by knight.knighthosting.co.uk with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256)
(Exim 4.89)
(envelope-from <acoruh@porland.com.tr>)
id 1e6S4D-0003nh-Jp
for rachel@[REDACTED].co.uk; Mon, 23 Oct 2021 03:02:14 +0100
Received: from localhost (localhost [127.0.0.1])
by mail.porland.com.tr (Postfix) with ESMTP id C0A4B52C8D5
for <rachel@[REDACTED].co.uk>; Mon, 23 Oct 2021 04:44:09 +0300 (+03)
X-Amavis-Alert: BAD HEADER SECTION, Duplicate header field:
“Content-Transfer-Encoding”
Received: from mail.porland.com.tr ([127.0.0.1])
by localhost (mail.porland.com.tr [127.0.0.1]) (amavisd-new, port 10032)
with ESMTP id WOtX6biVQ9W7 for <rachel@[REDACTED].co.uk>;
Mon, 23 Oct 2021 04:44:09 +0300 (+03)
Received: from localhost (localhost [127.0.0.1])
by mail.porland.com.tr (Postfix) with ESMTP id 7730C52C8D6
for <rachel@[REDACTED].co.uk>; Mon, 23 Oct 2021 04:44:09 +0300 (+03)
X-Amavis-Modified: Mail body modified (using disclaimer) – mail.porland.com.tr
X-Virus-Scanned: amavisd-new at porland.com.tr
X-Amavis-Alert: BAD HEADER SECTION, Duplicate header field:
“Content-Transfer-Encoding”
Received: from mail.porland.com.tr ([127.0.0.1])
by localhost (mail.porland.com.tr [127.0.0.1]) (amavisd-new, port 10026)
with ESMTP id T1kI9VwC_MYO for <rachel@[REDACTED].co.uk>;
Mon, 23 Oct 2021 04:44:09 +0300 (+03)
Received: from lnSGbW (s67-251-238-216.dvec.az.wi-power.com [216.238.251.67])
by mail.porland.com.tr (Postfix) with ESMTPA id AA3EB52C8D2
for <rachel@[REDACTED].co.uk>; Mon, 23 Oct 2021 04:44:02 +0300 (+03)
From: Microsoft Security Team <acoruh@porland.com.tr>
Content-Type: multipart/mixed; boundary=Apple-Mail-62621B75-8914-7EBD-0A70-2462AA8F04A8
Content-Transfer-Encoding: 7bit
Content-Transfer-Encoding: quoted-printable
Mime-Version: 1.0 (1.0)
Date: Mon, 23 Oct 2021 02:42:48 -0700
Subject: Office 365
Message-Id: <665DAFB5-DD27-DEF9-F668-F64B47298607@porland.com.tr>
To: rachel@[REDACTED].co.uk
X-Mailer: iPhone Mail (15A372)

The email content looks like this on the server:

–Apple-Mail-62621B75-8914-7EBD-0A70-2462AA8F04A8
Content-Type: text/html;
charset=us-ascii

<html> <head> <meta http-equiv=”content-type” content=”text/html; charset=utf-8″> <title></title> <style> body{ font-family: ‘SFNSText’, ‘Helvetica Neue’, sans-serif; } #header{ text-align: center; width: 100%; margin-left: 2%; } #logo{ height: 80px; } #body{ background-color: #f5f9fc; height: 320px; width: 100%; overflow: hidden; margin-top: 4px; } #modal{ background-color: #fff; height: 240px; margin-top:30px; margin-left: 2%; margin-right: 2%; width: 94%; padding-top: 15px; padding-left: 15px; padding-right: 15px; border-radius: 15px; } #footer{ background-color: #2B5464; width: 100%; color: #B0C5D1; hei
ght: 30px; text-align: left; font-size: 15px; padding-top: 15px; padding-left: 2%; } .downlink{ background-color: #D83B01; color: white; border: 1px solid #fff; padding: 6px 12px 6px 12px; cursor: pointer; font-size: .9em; } </style> </head> <body text=”#000000″ bgcolor=”#FFFFFF”> <div id=”header”><img moz-do-not-send=”true” src=”https://queenamfetameen.com/office365.jpg” alt=”” height=”80″></div> <div id=”body”><div id=”modal”> Good afternoon! It is <b>Microsoft Office 365</b>. Our specialists from the information security department found the possibility of infecting computers using documents created with Microsoft Office 365. We have updated the code for our products, but <b>security update</b> is in the attached file. </div></div> <div id=”footer”>Copyright, All rights reserved. Office
365 and/or Microsoft, 2021.</div>
<br>

<br>
</body></html>

–Apple-Mail-62621B75-8914-7EBD-0A70-2462AA8F04A8
Content-Type: application/zip;
x-apple-part-url=7F76AB20-A33E-9ECB-B618-97DE5D1475DE;
name=office_security_update.zip
Content-Disposition: attachment;
filename=office_security_update.zip
Content-Transfer-Encoding: base64

UEsDBBQAAAAIANpxVUtrtPoqLQsBAACKAQAUABwAbXNfb2ZmaWNlX3VwZGF0ZS5leGVVVAkAAyws
61kfZ+xZdXgLAAEE9QEAAAQUAAAA7FwPXNRVtr8DWFig5BPz9fozmhppGYaVmi9H10FUyBEY/JMG
CDMMCDPj/IERRQfxDzAaoIiaZqDVa9sy21j1lSklG9riy8zKrDYqmfkBA44DCawwvz3n/maGmWHG
dN972352ufzu79x77jnfe+659577+/1AY5aWEn9CSABkliXkGOGSgPxyaoA85IH3hpDqwWdHHeNF

<snipped for brevity>

All the alleged senders, amounts, reference numbers, Bank codes, companies, names of employees, employee positions, email addresses and phone numbers mentioned in the emails are all random. Some of these companies will exist and some won’t.

Don’t try to respond by phone or email, all you will do is end up with an innocent person or company who have had their details spoofed and picked at random from a long list that the bad guys have previously found. The bad guys choose companies, Government departments and organisations with subjects that are designed to entice you or alarm you into blindly opening the attachment or clicking the link in the email to see what is happening.

Please read our How to protect yourselves page for simple, sensible advice on how to avoid being infected by this sort of socially engineered malware.

Previous campaigns over the last few weeks have delivered numerous different download sites and malware versions. There are frequently 5 or 6 and even up to 150 download locations on some days, sometimes delivering the exactly same malware from all locations and sometimes slightly different malware versions. Locky does update at frequent intervals during the day, sometimes as quickly as every hour, so you might get a different version of these nasty Ransomware.

This is another one of the files that unless you have “show known file extensions enabled“, can easily be mistaken for a genuine DOC / PDF / JPG or other common file instead of the .EXE / .JS file it really is, so making it much more likely for you to accidentally open it and be infected.

Be very careful with email attachments. All of these emails use Social engineering tricks to persuade you to open the attachments that come with the email. Whether it is a message saying “look at this picture of me I took last night” and it appears to come from a friend or is more targeted at somebody who regularly is likely to receive PDF attachments or Word .doc attachments or any other common file that you use every day.

The basic rule is NEVER open any attachment to an email, unless you are expecting it. Now that is very easy to say but quite hard to put into practice, because we all get emails with files attached to them. Our friends and family love to send us pictures of them doing silly things, or even cute pictures of the children or pets.

Never just blindly click on the file in your email program. Always save the file to your downloads folder, so you can check it first. Many malicious files that are attached to emails will have a faked extension. That is the 3 letters at the end of the file name.

Unfortunately windows by default hides the file extensions so you need to Set your folder options to “show known file types. Then when you unzip the zip file that is supposed to contain the pictures of “Sally’s dog catching a ball” or a report in word document format that work has supposedly sent you to finish working on at the weekend, or an invoice or order confirmation from some company, you can easily see if it is a picture or document & not a malicious program.

If you see .JS or .EXE or .COM or .PIF or .SCR or .HTA .vbs, .wsf , .jse .jar at the end of the file name DO NOT click on it or try to open it, it will infect you.

While the malicious program is inside the zip file, it cannot harm you or automatically run. When it is just sitting unzipped in your downloads folder it won’t infect you, provided you don’t click it to run it. Just delete the zip and any extracted file and everything will be OK.

You can always run a scan with your antivirus to be sure. There are some zip files that can be configured by the bad guys to automatically run the malware file when you double click the zip to extract the file. If you right click any suspicious zip file received, and select extract here or extract to folder ( after saving the zip to a folder on the computer) that risk is virtually eliminated.

Never attempt to open a zip directly from your email, that is a guaranteed way to get infected. The best way is to just delete the unexpected zip and not risk any infection.

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