Some Changes To Remcos Rat Persistence Method

Some Changes To Remcos Rat Persistence Method

It looks like we are seeing a few changes to the Remcos RAT install & persistence method. Over the last couple of weeks I have noticed a few tweaks to the persistence & auto start of several Remcos Rat versions. Today it has changed again to try to bypass protections.

This all starts with the usual spam email, today’s ( or rather last night’s) was a fake invoice in a .iso / .img container. As you c an see from the virustotal reports .img containers are generally pretty poorly detected so are more likely to bypass perimeter defences.

Once the victim extracts the .exe file from the container which is more difficult to do in W7 but simply double clicking in W8.1 or W10 will allow the .exe file to be easily run. Because this .exe file has an icon that looks like an Adobe PDF file, it can very easily be mistaken for a genuine PDF. unless you have “show known file extensions enabled“. Why on earth Microsoft still insist after 20 years of hiding file extensions to dumb down the GUI is totally beyond me & many other researchers.

Once the .exe runs it copies itself to C:\Users\admin\AppData\Roaming\TAPI\chkntfs.exe ( The folder inside the roaming folder as will the .exe file name will be different on every computer, where the malware chooses a semi-random name based on a legitimate windows service or file that is normally found on most computers. This also drops a vbs in same folder autorunning the .exe file.

The biggest difference I am seeing today is that it also drops an internet shortcut in the windows start up folder, so the shortcut will run on every boot and start the vbs which runs the .exe. However the criminals behind this RAT / keylogger do play around with different file locations & persistence methods on a very frequent basis.
You can see all this quite clearly on the Anyrun report

Invoice.img : Extracts to: INVOICE.EXE Current Virus total detections [email] [img] [exe] : Anyrun |
This malware C2 are and it also appears to try to contact which is routed to ( Local host). All 3 of these are free no IP dns services so we can’t find the actual C2 easily

You can now submit suspicious sites, emails and files via our Submissions system 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. In fact that domain is for sale as a premium domain name for quite high $$$$

One of the emails looks like:
From: IOUU LLC <>
Date: Sat 21/09/2019 21:54
Subject: Your account is long over due!
Attachment: Invoice.img

Body Content:

First Reminder!
A review of our records indicates that your account is long over due. The attached invoice is now due for the past 10 days.

If payment has been made, could you specifically inform us when this was done so we could update our records.
If you have any query regarding this matter, please don’t hesitate to contact me.

Kind regards.

Email Headers:

IP Hostname City Region Country Organisation  Quezon City Metro Manila PH AS6364, Inc.  Hampden Sydney Virginia US AS8075 Microsoft Corporation

Note: Only the final IP address outside of your network in the Received: fields can be trusted as others can be spoofed

Received: from [] (port=40480 helo=freeerver)
	by with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256)
	(Exim 4.92)
	(envelope-from <>)
	id 1iBnxq-0000MK-PI
	for; Sat, 21 Sep 2019 23:34:51 +0100
Received: from (unknown [])
	(using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits))
	(No client certificate requested)
	by freeerver (Postfix) with ESMTPSA id D376C84C882;
	Sat, 21 Sep 2019 16:53:37 -0400 (EDT)
Content-Type: multipart/mixed; boundary="===============0679614698=="
MIME-Version: 1.0
Subject: Your account is long over due!
To: Recipients <>
From: "IOUU LLC" <>
Date: Sat, 21 Sep 2019 20:53:36 +0000
X-Priority: 1 (High)
Sensitivity: Private

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.

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.
Main object- “{Possible Spam } Your account is long over due!.msg”
sha256 b78faefe577c3f09b35c6b4a81b1fd4c7d70154ab7589eda988be73d036e4866
sha1 8d8d80eeda3a2a4f33aba72db50affab5d265caf
md5 42b21fef9742a35830c03f3ee199f2f8
Dropped executable file
sha256 C:\Users\admin\Desktop\Invoice.exe cd0cb55cdfadf33c66ad74cb1c03da7f661c5a99cbf090c60790d9543f36cb74
DNS requests