New Agenttesla Keylogger Install Method – Choice.exe

Malspam

We continue to see AgentTesla keylogger / Infostealer on a daily basis. The UK generally has been fairly quiet for malware over the last few months ( since Easter 2019) and we are only seeing the “commodity” malware like AgentTesla, Hawkeye, Nanocore, Lokibot etc on a very frequent basis.

Over the last week or 10 days we have noticed a slight change in the delivery / install method for AgentTesla. They are using choice.exe silently to install the malware.

Choice.exe is a Microsoft default file in all current Microsoft OS versions that is supposed to be used with bat files so a user can select an option from a list with single button presses. It is intended to display an alpha-numeric menu with the options beside it ( press 1 etc). This version of AgentTesla is “living off the land” and abusing this.

I don’t see any dropped bat files in the anyrun reports on this.

The bad actors are sticking to the generic order/invoice emails. Today’s version is using a .exe file inside a .iso container, but we see also zip / rar / ace / img containers as well.

You can now submit suspicious sites, emails and files via our Submissions system
Neither TSK Equipment Co Ltd or beatty.com have 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

PO.order67676237.scan.pdf…iso ( virusTotal) : Extracts to: PO.order67676237.scan.pdf…exe Current Virus total detections: Anyrun |

The C2 on this one is mail.chinaclassic.com.sg 69.90.162.15 ( I cannot easily determine the email addresses being used for exfiltration of the stolen data because the criminals are using STARTTLS to encrypt the entire communication chain including sending & receiving addresses) This LINK explains the differences between various email encryption methods.

One of the emails looks like:

From: TSK Equipment Co Ltd <lobuntoro@beatty.com>

Date: Fri 26/07/2019 19:19

Subject: Confirm Order_67676237

Attachment: PO.order67676237.scan.pdf…iso

Body content:

Dear

How are you doing? Kindly note that my colleague Mr Kelvin already left our company due to her personalReason and I will take over his job from now on Please confirm the delivery time for the attached Order.Shipment will be to former address. Feel free to contact us if more details are required. Holiday Note: Our office will be closed from 2/Aug – 10/Aug for holiday. Thanks & Best regards, Phillip ChenPurchasing Manager TSK Equipment Co Ltd 33, Cheng Gung St., Min Hsiung Ind. Park,Minhsiung Hsiang, 62157 Tel: +106 2 3529 0095 EXT.22Fax: +106 2 2783 8893Email:gsk@gsk_equipment.com /gskequipment@gmail.com

Screenshot:

Fake Order email

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.

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.

:

IOC:

Main object- “PO.order67676237.scan.pdf.iso”
sha256 a638973bf1fa8783c5b4bc7f36e35de1f0035a4b778088f570a43e81a4840e0b
sha1 928dbe89cd6700cdc1b25e6c0a54934a5e96fdab
md5 db31ebf07e01052569566e404055cb47
Dropped executable file
sha256 C:\Users\admin\Desktop\PO.order67676237.scan.pdf…exe 6b3d817cafce69de13ea2fb73360a7707ae2a3e8bf216e9280c39bcba79c1d7e
DNS requests
domain checkip.amazonaws.com
domain mail.chinaclassic.com.sg
Connections
ip 192.35.177.64
ip 52.6.79.229
ip 69.90.162.15
HTTP/HTTPS requests
url http://checkip.amazonaws.com/