Unmasking Emotet: The Persistent Threat in Cyberspace

Emotet is a Trojan that primarily spreads through spam emails, also known as malspam. This advanced persistent threat (APT) malware is highly sophisticated and very difficult to combat due to its modular nature and worm-like features that enable network-wide infections. The infection may arrive either via malicious script, macro-enabled document files, or a malicious link. The emails containing Emotet may even carry familiar branding, designed to look like a legitimate email, tricking the recipient into interacting with the harmful content.

Once Emotet is installed on a system, it can steal personal information, spread to other systems on the network, and download additional malware. This makes Emotet a significant threat to both businesses and individuals, and it is known for being one of the most costly and destructive types of malware, costing upwards of $1 million per incident to clean up.

Emotet is a modular malware, which means that it consists of several different components that can be customized and updated by the malware’s developers. This constant evolution makes it particularly challenging for antivirus software to detect and remove. Furthermore, Emotet is known to cooperate with other malware strains, such as TrickBot and Ryuk, to launch more sophisticated attacks.

Over the years, Emotet has evolved from a banking trojan to a distributor of other types of malware. This evolution is a testament to the adaptability and tenacity of the cybercrime group behind Emotet, tracked as TA542 (aka Gold Crestwood or Mummy Spider). The group is known for adding new modules to Emotet’s arsenal, such as an SMB spreader designed to facilitate lateral movement using a list of hard-coded usernames and passwords, and a credit card stealer that targets the Chrome web browser.

Emotet’s evolution has also seen changes in the way it spreads. While the use of macros has been a common method for payload distribution and initial infection, recent campaigns have adopted new tactics to sneak past malware detection tools. For instance, new variants of Emotet have moved from 32-bit to 64-bit as an additional method for evading detection. These new tactics demonstrate Emotet’s persistent attempts to retool itself and propagate other malware.

Emotet’s activities have a significant impact on businesses and organizations. In 2022 alone, SecurityHQ observed over 266 incidents related to Emotet that were handled and remediated globally. Interestingly, Emotet does not operate all year round. Instead, it launches campaigns, takes breaks, and then returns with a vengeance. This pattern keeps organizations on their toes, as they must always be prepared for the next wave of attacks.

Emotet’s activities are often linked to spikes in ransomware attacks. Wherever Emotet activity spiked, there was also a notable increase in ransomware incidents. This trend underscores the gravity of the threat that Emotet poses, as it is often used as a gateway to introduce even more damaging malware, including ransomware.

Protecting yourself from Emotet requires a multi-faceted approach. You should be careful about what emails you open and what links you click on. Keep your antivirus software up to date and install a firewall, ensuring it is always enabled. Use strong passwords and change them regularly. Furthermore, stay informed about the latest threats and how to protect yourself.

Emotet is a serious threat, but by taking proactive measures, you can help to keep your computer and network safe.

The Emotet malware operation is attributed to a cybercrime group known as TA542, also referred to as Gold Crestwood or Mummy Spider. This malware operation has refined its tactics over the years to elude detection while also acting as a conduit for other dangerous malware such as Bumblebee and IcedID​¹​.

Emotet, which officially reemerged in late 2021, distributes itself via phishing emails and has evolved from a banking trojan to a malware distributor since its first appearance in 2014​²​. The malware operation is modular, capable of deploying various components that can exfiltrate sensitive information from compromised machines and conduct other post-exploitation activities. Recent campaigns have relied on generic lures with weaponized attachments to initiate the attack chain​³​​⁴​.

Technically, Emotet has adapted to using Microsoft OneNote documents embedded with VBScript files to install the malware, as a response to Microsoft’s implementation of macro-blocking in their Office Suite. The OneNote documents prompt users to click a button to view the complete contents, which triggers the execution of a malicious Windows Script File (WSF) when the target clicks the button. This WSF conceals a VBScript downloader that fetches the Emotet binary payload from what is likely a compromised website. The payload is typically encrypted and concealed within a .zip file to further evade detection. Once downloaded, the payload is decrypted and extracted, revealing the Emotet binary in the form of a .DLL file. The malware then uses the “regsvr32.exe” utility to execute the DLL, launching the malicious payload. This technique is known as “DLL side-loading” and is commonly used by threat actors to bypass typical security measures​⁵​​⁶​.

Once installed, Emotet establishes persistence by creating an AutoStart registry key pointing to the binary located. It also collects data such as contacts, emails, and credentials from the infected machine to expand its target base. It has also been observed dropping additional payloads such as Cobalt Strike (for lateral movement), Quantum ransomware, and BlackCat ransomware​⁷​​⁸​​⁹​.

Mitigation against Emotet involves a multi-layered approach:

1. User Awareness and Training: Establish a robust Security Awareness Program to educate users on recognizing phishing emails, malicious tactics, and other social engineering techniques employed by TA542​¹⁰​.
2. Email Filtering and Spam Protection: Implement strong email filtering and spam protection measures to minimize the probability of Emotet-related malspam reaching users’ inboxes​¹¹​.
3. Scripting Monitoring and Restriction: Monitor the usage of PowerShell and other scripting languages, imposing execution restrictions where necessary, as Emotet is known to exploit these tools during the infection process​¹²​.
4. Application Whitelisting: Employ application whitelisting solutions to control which applications are permitted to execute on your organization’s systems, preventing unauthorized or malicious applications, such as Emotet and its associated payloads, from running on endpoints​¹³​.

Emotet is a malware operation that has continued to evolve and refine its tactics to avoid detection. It acts as a conduit for other dangerous malware such as Bumblebee and IcedID and is distributed via phishing emails. It has evolved from a banking trojan to a malware distributor since its first appearance in 2014. Emotet is also modular, capable of deploying an array of proprietary and freeware components that can exfiltrate sensitive information from compromised machines and carry out other post-exploitation activities​¹​​²​.

Recent spam email campaigns associated with Emotet have used .XLS files with a new method for tricking users into allowing macros to download the dropper. In addition, new Emotet variants have moved from 32bit to 64bit, as another method for evading detection​³​.

Emotet presents a persistent threat to organizations worldwide. It often pauses campaigns for significant amounts of time, then returns with a new tactic. Emotet not only resurged in 2022, but continues to deploy sophisticated malware, including ransomware post-compromise. Specifically, ransomware groups, such as Conti, Quantum Locker, and ALPHV, were observed using Emotet to distribute their ransomware payloads​⁴​.

The technical analysis of recent Emotet activity shows that it uses various techniques to infect systems. In a recent example, Emotet leveraged a W-9 form as a lure to download malicious Office documents, which were designed to impersonate communications from the IRS. In response to Microsoft’s security measures, Emotet has shifted to using Microsoft OneNote documents embedded with VBScript files to install itself. Once the Emotet payload is downloaded, decrypted, and extracted as a DLL, the malware uses the “regsvr32.exe” utility to execute the DLL, which subsequently launches the malicious payload. This technique is known as “DLL side-loading” and is a common method used by threat actors to bypass typical security measures​⁵​​⁶​.

Once Emotet is on a system, it establishes persistence on the infected system by creating an AutoStart registry key pointing to the binary located. The malware typically collects data, such as contacts, emails, and credentials, from the infected machine. These are then used to expand its target base, including the injection of malspam into existing email chains. Security researchers have recently seen Emotet drop additional payloads including Cobalt Strike (for lateral movement), Quantum ransomware, and BlackCat ransomware​⁷​​⁸​​⁹​.

To defend against Emotet, organizations are advised to establish a robust Security Awareness Program, implement strong email filtering and spam protection measures, closely monitor the usage of PowerShell and other scripting languages within the organization, imposing execution restrictions where necessary, and employ application whitelisting solutions to control which applications are permitted to execute on the organization’s systems​¹⁰​.