As soon as used solely by the cybercriminals behind REVil ransomware and the Gootkit banking trojan, GootLoader and its main payload have advanced into an preliminary entry as a service platform—with Gootkit offering info stealing capabilities in addition to the aptitude to deploy post-exploitation instruments and ransomware.
GootLoader is understood for utilizing SEO (Search engine optimization) poisoning for its preliminary entry. Victims are sometimes enticed into clicking on malicious adware or hyperlinks disguised as authentic advertising and marketing, or on this case a authentic Google search directing the consumer to a compromised web site internet hosting a malicious payload masquerading as the specified file. If the malware stays undetected on the sufferer’s machine, it makes means for a second-stage payload generally known as GootKit, which is a extremely evasive information stealer and distant entry Trojan (RAT) used to ascertain a persistent foothold within the sufferer’s community surroundings. GootKit can be utilized to deploy ransomware or different instruments, together with Cobalt Strike, for follow-on exploitation.
Detection of a brand new GootLoader variant actively being utilized by adversaries earlier this yr led to a broad risk searching marketing campaign by Sophos X-Ops MDR for GootLoader cases throughout buyer environments. As is typical of Gootloader, the brand new variant was discovered to be utilizing Search engine optimization poisoning—the usage of SEO ways to place malicious web sites managed by GootLoader’s operators excessive within the outcomes for particular search phrases—to ship the brand new, JavaScript-based Gootloader package deal. On this case, we discovered the GootLoader actors utilizing search outcomes for details about a specific cat and a specific geography getting used to ship the payload: “Are Bengal Cats authorized in Australia?”
In the course of the risk hunt marketing campaign, MDR found a .zip archive used to ship GootLoader’s first-stage payload whereas reviewing an impacted consumer’s browser historical past. This allowed MDR to determine the compromised web site that was internet hosting the malicious payload. This report highlights the MDR investigation course of and the technical particulars of the uncovered GootLoader marketing campaign.
Technical Evaluation and Identification
First-stage payload
On March 27, 2024, the MDR staff carried out a proactive risk searching marketing campaign throughout a number of clients estates, following lately reported identification of a brand new GootLoader variant being actively exploited within the wild.
Our investigation revealed the risk actor was utilizing Search engine optimization poisoning by an simply accessed on-line discussion board discovered through a easy Google search, initiated by the consumer for ‘Do you want a license to personal a Bengal cat in Australia’. The primary search end result took us to this URL:
hxxps[://]ledabel[.]be/en/are-bengal-cats-legal-in-australia-understanding-the-laws-and-regulations/#:~:textual content=Eachpercent20statepercent20andpercent20territorypercent20in,topercent20keeppercent20thempercent20aspercent20pets.
Instantly after the consumer clicks the hyperlink, a suspicious .zip file was downloaded to C:Customers
Second-stage payload
Upon assessment of the working processes, we have been capable of decide {that a} small JavaScript file was dropping a big JavaScript file on the location C:Customers
We moreover noticed the creation of a scheduled job named “Enterprise Aviation” with the command line “wscript REHABI~1.JS” (as proven in Determine 3). This was suspected to be a persistence technique through which the risk actor was using WScript.exe to execute the second-stage payload of GootKit.
We additionally famous the utilization of the command C:WindowsSystem32cscript.exe REHABI~1.JS spawning PowerShell.exe, as proven in Determine 4. The cscript.exe command line instrument is restricted to Home windows Server. The instructions handed to PowerShell weren’t captured on this case.
Nevertheless, inspecting the URL historical past, we noticed PowerShell.exe reaching out to the next domains, as proven in Determine 5. Third-stage payload
Within the case the MDR staff examined, our staff didn’t observe the third stage being profitable in reaching a full deployment of GootKit, stopping the obtain of any extra malicious tooling. This stage usually is the place the deployment of extra instruments equivalent to Cobalt Strike happens, or when ransomware is added to the sufferer’s machine.
Malware Triage
Static Evaluation
MDR carried out a static evaluation of the of the .zip pattern obtained from the malicious URL hxxps[://]ledabel[.]be/en/are-bengal-cats-legal-in-australia-understanding-the-laws-and-regulations/#:~:textual content=Inpercent20mostpercent20casespercent2Cpercent20youpercent20do,apercent20Bengalpercent20catpercent20inpercent20Australia. Inside the zip file was a JavaScript named “are bengal cats authorized in australia 72495.js”.
As we famous above, the JavaScript’s identify is modified every time the file is downloaded with a special concluding numerical sequence. This was additionally noticed when extracting the small JavaScript from the zip file, as proven in Determine 6. For instance, customers could observe a filename with are bengal cats authorized in australia 75876.zip as an alternative, when making an attempt to acquire a pattern from the malicious URL.
A string evaluation of the dropped file was not helpful in figuring out its intent, because the JavaScript was closely obfuscated—as is frequent in Gootloader samples. The script additionally included boilerplate licensing feedback to make it seem like a authentic JavaScript, as proven in Determine 7.
Nevertheless, Strings evaluation of the secondary bigger JavaScript that was downloaded into C:Customers
MDR used a Python script created by Mandiant for auto-decoding of GootLoader JavaScript to statically analyze the initially downloaded Are_bengal_cats_legal_in_australia_72495.js. As proven in Determine 9, the file was recognized as Gootloader variant 3.0 by the obfuscation technique, the place the primary file created was named Huthwaite SPIN promoting.dat adopted by Small Items Techniques.js and Scheduled Process named Vacation spot Branding. The decoder additionally recognized varied malicious domains throughout the obfuscated strings.
Dynamic evaluation
Varied dynamic evaluation instruments have been utilized to look at the conduct of the malicious JavaScript. Upon execution, WScript.exe was noticed creating the primary file situated inside C:Customers
Shortly after Wscript.exe executed Are_bengal_cats_legal_in_australia_72495.js, Course of Hacker confirmed CScript.exe and Powershell.exe being created with a conhost.exe spawned, as proven in Determine 11. MDR noticed that Wscript.exe would terminate, adopted by Cscript.exe that might additionally terminate shortly after, after which Powershell.exe was created.
Persistence was obtained through CScript.exe executing the file SMALLU~1.js through a scheduled job named Vacation spot Branding (with command line wscript SMALLU ~1.js , as proven in Determine 12). In the course of the lab evaluation, the secondary JavaScript could be dropped inside any folders situated inside C:Customers
MDR carried out community and C2 examinations utilizing Wireshark and FakeNet to carry out a community seize throughout the execution of Are_bengal_cats_legal_in_australia_72495.js. FakeNet confirmed varied domains being reached out to with GET /xmlrpc.php HTTP/1.1 requests through Powershell.exe. The requests contained Base64-encoded cookies which, when decoded, confirmed enumeration info relating to machine directories and host info such because the folder path of C:Customers
Examination of the PCAP seize lists varied domains that have been additionally recognized throughout static evaluation, as proven in Determine 14. These domains and IOCs have been categorised by Sophos Labs as malware/callhome ; the preliminary and secondary JavaScript recordsdata are categorised as JS/Drop-DIJ and JS/Gootkit-AW respectively.
MITRE mapping
The next chart maps the noticed ways to the MITRE ATT&CK® framework.
| Tactic | Approach | Sub-Approach | ID |
| Reconnaissance | |||
| Useful resource Improvement | Stage Capabilities | Add Malware
Search engine optimization Poisoning |
T1608.001
T1608.006 |
| Preliminary Entry | Drive-by Compromise | T1189 | |
| Execution | Command and Scripting Interpreter | JavaScript | T1059.007 |
| Persistence | Scheduled Process/Job | Scheduled Process | T1053.005 |
| Privilege Escalation | |||
| Protection Evasion | Obfuscated Recordsdata or Data | Embedded Payloads | T1027.009 |
| Credential Entry | |||
| Discovery | System Data Discovery | T1082 | |
| Lateral Motion | |||
| Assortment | |||
| Command and Management | |||
| Exfiltration | Exfiltration Over Internet Service | T1567 | |
| Affect |
Conclusion
GootLoader is one in all numerous persevering with malware-delivery-as-a-service operations that closely leverage search outcomes as a method to achieve victims. The usage of SEO, and abuse of search engine promoting to lure targets to obtain malware loaders and dropper, usually are not new—GootLoader has been doing this since not less than 2020, and we’ve noticed Raccoon Stealer and different malware-as-a-service operations doing the identical for simply as lengthy. However we’ve seen continued progress on this strategy to preliminary compromise, with a number of huge campaigns utilizing this system over the previous yr.
Sophos endpoint safety blocks GootLoader by numerous behavioral and malware-specific detections. However customers ought to nonetheless look out for search outcomes and search commercials that appear too good to be true on domains which are off the overwhelmed path—whether or not they’re seeking to get a Bengal Cat or not.
Indicators of Compromise
An inventory of IOCs is offered as a CSV file within the Sophos GitHub repository right here.
