Emotet did what it did best – delivered weaponized Word files via email, carrying macros that – if enabled – triggered downloading malicious payloads from third-party websites. The delivered file has been “pumped” – bloated to a large size. This helps it avoid activating anti-virus software. Emotet uses different methods to “pump” the file – sometimes only zeros are added to the end of the document and sometimes the entire paragraph of Moby Dick is copied and pasted – into a white font on a white background, so they cannot be seen.
Cybersecurity researchers at Deep Instinct recently discovered a new variant of the notorious malware and announced that it has been updated with some new tricks that help it avoid being hit by anti-malware programs.
On average, the file is more than 500MB in size, the researchers say. Files of this size are usually not scanned by anti-virus programs.
The document content is also blurred, with the message superimposed that “document is protected” – to trick the victim into activating the macro.
If this happens, the Word document will download a malicious .DLL file that has also been “pumped”. The DLL hosted on a legitimate third-party website has been hacked and is being used as a trick – to spread malware.
If a victim accidentally downloads Emotet, they scan the endpoint for passwords and other sensitive data, and extract it to a remote location.
Moreover, it will use the compromised device to spread to more victims. As noted earlier, Emotet is often spread by email, exploiting existing email chains and replying to previous messages so as not to raise suspicion. In the email, Emotet will also call the victim’s name. Finally, the botnet is capable of downloading additional malicious payloads, such as the Ryuk ransomware or TrickBot malware.