Dridex Delivered Via Random Subjects With Cab Files

spotting malware

The next in the never ending series of malware downloaders is an email with a variety of subjects along the lines of Form Sydnee I. Hahn ( initial word is either Form / Token / License / Certificate or other similar word followed by a name that matches the name in the body of the email) coming as usual from random companies, names and email addresses with a semi-random named cab file attachment ( that matches the subject word ) containing a .JS file ( cab files are Microsoft specific archives ( zip files) that are normally used for windows updates.

Almost any unzipping tool will extract them, however windows explorer will natively extract and autorun any content inside a cab file if double clicked to open them. This looks like Dridex today, rather than the Locky ransomware we are so used to seeing in UK

Update 09.30 UTC a second run starting with a mix of .cab files and .zip files. possibly because many mail filtering systems including Mail Scanner (https://www.mailscanner.info/) used on a high proportion of Linux mail servers detects and warns about .cab files by default. Some servers are set to block them automatically. This server is set to warn about potentially dangerous file extensions but not block them ( to certain domains only ) so I can obtain malware samples to warn / alert and submit to anti-virus companies and help protect everybody. For every cab file that I have received so far, I also got a warning message to my postmaster / admin email address

The more unusual things about this Dridex malspam run is 1) they are coming in smaller waves than usual , only 10 -15 per domain instead of the usual hundreds, perhaps as a test run to see if they have got it right. 2) Every copy I have seen so far today, all sent to different domains contacts / downloads from the same location http://www.mobilemanager.fr/log.khp which makes it quite easy for an admin to block. It looks like it has been hacked, rather than set up as a distribution site. I recommend blocking its IP 217.76.132.43

The sort of subjects we are seeing include:

  • Form Sydnee I. Hahn
  • Token Jolie T. Barrett
  • License Armando H. Bates
  • Certificate Brittany T. Beach
  • Archive Linda K. McLaughlin
  • Papers Sylvia C. Price
  • Agreement Dieter U. Vinson
  • Report David W. Rogers
  • Document Isaac Q. Lucas

 

They use email addresses and subjects that will entice a user to read the email and open the attachment. A very high proportion are being targeted at small and medium size businesses, with the hope of getting a better response than they do from consumers.

One of the emails looks like:

From: HilariSydnee I. Hahn <rtep.springvale@ljh.com.au>

Date: Tue 11/10/2021 08:03

Subject: Form Sydnee I. Hahn

Attachment: Form.cab

Body Content:

Good morning

Please review your Form.

I’m waiting for your reply

Kindest regards

Sydnee I. Hahn

An alternative body content

Hi

Here is your Token.

Pls inform me the answer as soon as posible

Regards

Jolie T. Barrett

An alternative body content

Greetings

Here is your License.

I’m still waiting for your answer

Cain M. Rogers

Screenshot:

These malicious attachments normally have a password stealing component, with the aim of stealing your bank, PayPal or other financial details along with your email or FTP ( web space) log in credentials. Many of them are also designed to specifically steal your Facebook and other social network log in details. A very high proportion are Ransomware versions that encrypt your files and demand money ( about £350/$400) to recover the files.

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.

11 October 2016 : Form.cab : Extracts to: 20792.tmp Current Virus total detections: MALWR shows a download from http://www.mobilemanager.fr/log.khp which gave me 20792.tmp ( VirusTotal) Detections are inconclusive but Payload Security indicates that this is most probably Dridex banking Trojan, However that also shows an error in running the file with an unsupported system message. That might mean that there is a fault with the Dridex binary or more likely that the Dridex malware gang have added even more protections to their malware and stopping it running when a sandbox or VM is detected.

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. Dridex /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 or Banking password stealer Trojans.

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 (https://en.wikipedia.org/wiki/Social_engineering_(security)) 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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