The infamous data-stealing URSNIF malware has done it again and it's here to collect more keystrokes, login credentials, browsing activities, and other user activities. It continues to undress and dress itself differently, time and time again. Earlier this year, we saw it being distributed via SVG files to hide and embed JavaScript code. For the past few weeks, we have observed URSNIF being spammed again but using different e-mail details such as billing, MMS messages, and even hotel bookings. Here is a brief analysis of this latest campaign.

Translated to English:

Subject: Your bill

It's your bill.

Best regards,

Elise Devos

The attachment includes a .JS file or a .ZIP file which holds the malicious JavaScript.

Closely inspecting the attachment would show obfuscated JavaScript.

Once properly de-obfuscated, the code reveals that it downloads two executable binaries from:

hxxp://horcor.com/ese.tf

hxxp://www.nemcicenadhanou.cz/nvdtime.prs

Both ese.tf and nvdtime.prs are PE files even though they have a different file extensions and share the following hash details:

MD5: 23fb91262a83aed54abcebbf86e2af96

SHA1: 3bf342ec0a3aad1f4269c19eecf399be3afd4a94

These files are both NSIS compressed, which is a system used by developers to create Windows installers. Once properly decompressed and looking closer, you can spot Anti-VM code that tries to check for strings related to virtual machines and, if found, will cease any further execution of the malware with the purpose of avoiding sandbox execution or analysis. These are the same codes used by previous URSNIF variants.

URSNIF is using a new wave of mal-spam to propagate and is continuously evolving by using numerous ways to trick users to download files from their e-mails. The URSNIF threat actors also use script obfuscation, different file extensions, and even compress the binary differently to avoid malware detection.

Trustwave Secure Email Gateway can detect and block this threat at the gateway to avoid infection.