In a current technical investigation, researchers uncovered important insights into the infrastructure linked to a suspected Chinese language state-backed cyber actor known as “RedGolf.”
The group, also referred to as APT41, BARIUM, or Earth Baku, gained consideration following a report by Recorded Future’s Insikt Group in March 2023.
Their investigation revealed vital connections to more moderen campaigns, together with infrastructure related to mid-2024 assaults on Italian organizations.
Central to the evaluation was using historic Transport Layer Safety (TLS) certificates, which supplied distinctive identifiers and operational patterns tied to the continued exercise.
TLS Certificates Insights
The examination of GhostWolf’s infrastructure started with an in depth evaluation of 39 IP addresses linked to the menace actor as per the Insikt Group’s IoC dataset.
A important discovery concerned certificates from the wolfSSL library an open-source SSL/TLS library extensively utilized in embedded techniques and safe communications.
One key anomaly recognized was the modification of the Organizational Unit (OU) area in these certificates.
Whereas the professional instance certificates used “Consulting_1024,” the malicious certificates altered this to “Support_1024,” successfully creating a definite TLS fingerprint.
Additional, researchers utilized the Hunt SSL Historical past device to uncover 122 IP addresses related to this certificates’s SHA-256 hash.
A deeper refinement utilizing JA4X fingerprinting, a sophisticated extension of the JA3 TLS fingerprinting technique, narrowed outcomes to 41 distinctive IPs sharing an analogous configuration.
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Leveraging TLS Fingerprints and Certificates Evaluation
By combining a number of distinctive indicators, together with the anomalous OU area, certificates SHA-256 hash, and JA4X fingerprint, researchers crafted superior search queries to determine still-active infrastructure tied to GhostWolf.
Utilizing instruments equivalent to Hunt’s Superior Search, they pinpointed six lively IP addresses exhibiting constant traits.
These servers demonstrated coordinated conduct, working totally on HTTPS (port 443) or alternate ports equivalent to 8443.
Key observations included the reuse of internet hosting suppliers throughout geographies (e.g., The Fixed Firm, LLC, and Nebula World LLC).
Anomalies equivalent to overlapping IP ranges with beforehand recognized threats, together with Yoroi’s report on APT41 intrusions, added weight to suspicions of continuity in operations.
Investigators additionally recognized a server internet hosting a suspected variant of the GhostWolf certificates.
This server’s certificates resembled professional wolfSSL examples however exhibited timestamps carefully matching the Support_1024 infrastructure.
Though conclusive attribution to RedGolf stays elusive, its geographic location and internet hosting supplier align with beforehand reported Command-and-Management operations.
This evaluation underscores the persistence of menace actors like RedGolf/APT41.
Their continued use of modified certificates, constant internet hosting suppliers, and carefully assigned IP ranges signifies a deliberate effort to take care of infrastructure longevity whereas evading detection.
The findings spotlight the important function of TLS certificates evaluation and superior fingerprinting strategies in detecting and monitoring refined menace actors.
The reuse of refined certificates modifications, coupled with constant infrastructure setups, means that defenders should stay vigilant.
Repeatedly analyze TLS certificates for uncommon fields, equivalent to modified Organizational Models (e.g., Support_1024) or sudden situation dates.
Leverage enhanced fingerprinting instruments, like JA4+, to detect and isolate malicious server configurations from benign site visitors.
By adopting these measures, defenders can higher anticipate adversary exercise, mitigate dangers, and improve general community safety posture.
The investigation into GhostWolf’s infrastructure demonstrates the significance of persistent monitoring and historic knowledge evaluation in combating decided state-backed cyber threats.
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