GootLoader Hackers Are Compromising Employees of Law and Accounting Firms, Warns eSentire

GootLoader Gang Launches Wide-Spread Cyberattacks Enticing Legal and Accounting Employees to Download Malware

eSentire, the industry’s leading Managed Detection and Response (MDR) cybersecurity provider, is warning law and accounting firms of a wide-spread GootLoader hacker campaign. In the past three weeks and as recently as January 6, eSentire’s threat hunters have intercepted and shut down cyberattacks launched against three law firms and an accounting firm.  The GootLoader hacking group is behind the attacks. Ironically, these attacks coincide with the one-year anniversary of the GootLoader Gang’s December 2020 Website Poisoning Campaign, which eSentire first reported. GootLoader is a stealthy initial access malware, which after getting a foothold into the victim’s computer system, infects the system with ransomware or other lethal malware. Note: GootLoader previously had a rich history of spreading the REvil, a.k.a. Sodinokibi or Sodin ransomware, prior to law enforcement shutting down its operators. It was eSentire’s Atlas XDR platform that first alerted its threat hunters to nefarious activity on the endpoints of several client systems, and they quickly began to track, identify and shut down the GootLoader attacks.

Employees Must Remember the Adage: “There Is No Such Thing as a Free Lunch or a Free Business Agreement.”

GootLoader is spread via Drive-By-Download campaigns, fueled by Search Engine Optimization, specifically through Google. In these current attacks, as in previous GootLoader campaigns, the hackers are luring business professionals to legitimate but compromised websites that they have populated with hundreds of pages of content, which include numerous references to business agreements, including legal and financial agreements. The content purports to offer free samples of these documents for download. In fact, during the extensive GootLoader campaign that initiated last December, eSentire’s research team, the Threat Response Unit (TRU), found that the GootLoader hackers stood up over a 100,000 + malicious webpages promoting different types of business agreements. In one case, one of the compromised websites, was hosting 150 pages of the hackers’ content. 

One might ask how are the GootLoader threat actors able to insert hundreds of pages of malicious content into legitimate websites?  Unfortunately, it is far too easy. The GootLoader gang has identified dozens of legitimate websites using WordPress as their content management system.  WordPress, like many content management systems, has numerous vulnerabilities and the hackers are easily able to exploit these vulnerabilities and populate these websites with as many malicious pages as they desire, and all without the website owner’s knowledge. The TRU team discovered that these websites cover a wide range of industries including: hotel, high-end retail, education, healthcare, music and visual arts, among others.

“With the volume of content, the threat actors have populated onto the web, when a professional goes onto Google searching for a sample business agreement, the hackers’ malicious web pages come up in the top Google searches,” said Keegan Keplinger, research and reporting lead for TRU. “When the computer user navigates to one of these malicious web pages and hits the link to download the purported business agreement, they are unknowingly downloading GootLoader. As a result, unless your organization has security protections in place, your organization is likely infected with GootLoader, which could lead to a ransomware deployment, and then it is game over.” In this campaign, the titles of the business agreements which lured the employees of the three law firms were “Olympus Plea Agreement” (See Figure 1), “Post nuptial Agreement Puerto Rico” (See Figure 2), and “Model IP Agreement,” and the employee of the accounting firm was enticed in downloading what they thought was a financial agreement titled “Wayne County Payment Agreement.”

“Once infected with GootLoader, the typical objective is for ransomware or Cobalt Strike to be downloaded onto the victim’s computer,” continued Keplinger.  “Cobalt Strike is a full- featured intrusion suite. It originated as a legitimate remote access tool, developed for red teams to use in penetration testing. However, in the past year, it has become the cybercriminals’ primary means of turning a foothold, such as what GootLoader provides, into a hands-on intrusion. Hands down, it has become one of the favorite tools in the cybercriminals ‘arsenal.”  The Cobalt Strike suite includes everything required to run a cyber intrusion, from initial access (e.g. embedding the Cobalt Beacon in documents and exploits) to lateral movement (injecting credential stealers into legitimate windows processes, abusing shares, and leveraging administrative tools like PsExec and PowerShell). Additionally Cobalt Strike is highly customizable – settings can be changed to disguise Command and Control (C2) traffic and injection targets to avoid detection.

Figure 1: The GootLoader Hacking Group’s bogus web forum, purports to host a sample of the “Olympus Plea Agreement.”  When the malicious link is clicked on by the victim, they will be served the GootLoader malware.

Figure 2: A Google search showing the number one result for the title: “Postnuptial Agreement Puerto Rico.”  When the malicious link is clicked on by the victim, they are served the GootLoader malware.

Observations of the GootLoader Gang’s Malicious Drive-By-Download Campaign from Keegan Keplinger, TRU Security Researcher and Distinguished Security Professional

“GootLoader relies heavily on social engineering to establish its foothold, from poisoning Google search results to fashioning the payload, “said Keplinger. ”GootLoader’s operators invite employees to seek, download and execute their malware under the guise of a free business agreement template. This is particularly effective against legal firms, who may encounter uncommon requests from clients. The infamous financial Internet crime group, FIN7, is another group known to use social engineering to target law firms. In the case of FIN7, eSentire discovered last July that they were using public dockets from real court cases to craft spearphishing emails.”

“All organizations, not just law firms and accounting firms, should have a vetting process for business agreement samples, gathered from the Internet, to ensure that they are not infected with malware,” continued Keplinger. “Employees should also be aware that GootLoader comes as a JavaScript (.js) file.  While it is often disguised as a document, right clicking the downloaded file and clicking properties will show the real file type. Whenever downloading documents from the web, scripting files like .js, .ps1 and .cmd should never be executed.” (See Figure 3).

Figure 3: Computer steps for looking up the properties of a file.

Defending One’s Company and Employees Against GootLoader

The GootLoader hackers ensnare their victims because they fool them into downloading documents from the Web. Therefore, one of the most important defenses companies can implement against GootLoader is security awareness training for their employees.

• Companies must educate employees regarding the risk of GootLoader, and more broadly, the security risks involved with using Search Engines to discover free document templates
• Employees need to make sure they can trust document sources. Even legitimate Word and Excel documents from the Internet can lead to malware
  • Be wary of Word and Excel documents sent from an unknown source or acquired from the Internet that prompts you to ‘Enable Macros’
• Employees need to ensure that the content downloaded is content they intended to download. If one downloads a document from the Internet but they are served a JavaScript file, one should not open it. It should be escalated to one’s internal IT security team
• Ensure standard procedures are in place for employees to submit potentially malicious content for review
• Use Windows Attack Surface Reduction rules to block JavaScript and VBScript form launching downloaded content
• Employ an Endpoint Detection and Response (EDR) product

Keep Watch for GootLoader’s Indicators of Compromise (IOCs) and Modus Operandi (MO)

“It is critical for companies’ security teams to quickly identify and remediate GootLoader infections within their environment to prevent follow-on attacks and the deployment of more damaging malware such as ransomware or Cobalt Strike,” said Keplinger. “Being aware of the hacker group’s typical MO, e.g.: infection process and their IOCs are key to identifying and shutting down a GootLoader attack.

GootLoader’s Typical Infection Process:

1. User performs a web search for a document or document template
2. User clicks on search result leading to GootLoader landing page
3. Landing page presents a fake web forum and link to the requested document
4. User clicks on the presented link, receives a Zip archive
5. User opens the archive, finds a JavaScript file (.js extension) disguised as the requested document
6. User executes the JavaScript file by double-clicking it
7. Windows executes the JavaScript file using the Windows script host process, resulting in execution of the GootLoader malware

Current GoodLoader IOCs

If you’re not currently engaged with a Managed Detection and Response provider, we highly recommend you partner with us for security services to disrupt threats before they impact your business.

Want to learn more about how we protect legal firms globally? Connect with an eSentire Security Specialist.