The next in the never ending series of malware downloaders being sent from the Necurs botnet is a typical generic spam email with the subject of Copy of Invoice 487391( random numbers) pretending to come from Customer Service <[email protected]>. There is no attachment with these today, just a link in the email body to a variety of compromised sites

The link will always go to <site name>/invoice.html which uses an iframe to download a random numbered invoice.js from ( this site has been used in this malware campaign for at least 1 week now )

The js filed is different to the ones we have been seeing so far this week, they are much smaller ( about 5kb) and using trivially obfuscated reverse strings to “hide” the download sites

Sites I found are:

They use email addresses and subjects that will entice a user to read the email and follow the link .

Invoice-671398.js Current Virus total detections: Payload Security | HJGFjhece3.exe ( VirusTotal) ( Payload Security )

I cannot work out if this is Trickbot or Locky today so far. The behaviour so far seen doesn’t exactly match either malware. It might be damaged or not working properly or some sort of anti-sandbox /VM protection to it. My gut feeling is Trickbot based on similar behaviour over the last few days when run in a sandbox or VM

One of the emails looks like:

From: Customer Service <[email protected]>

Date: Thu 14/09/2021 09:03

Subject: Copy of Invoice 487391

Body Content:

Please download file containing your order information. If you have any further questions regarding your invoice, please call Customer Service. Please do not reply directly to this automatically generated e-mail message. Thank you. Customer Service Department

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.