SentinelLabs has identified several tools designed to target web servers with ransomware or to leverage cloud services to upload files before encrypting local files on an endpoint.
Cloud ransom attack mechanics
Cloud ransom attacks typically target cloud-based storage services, such as Amazon’s Simple Storage Service (S3) or Azure Blob Storage. While each implementation varies, a ransom attack requires the attacker to find an accessible storage service, copy the file contents to a destination controlled by the attacker, and then encrypt or delete the files from the victim’s instance.
Cloud service providers (CSPs) have implemented robust security mechanisms that minimise the risk of data being lost permanently. For example, AWS’ Key Management Service (KMS) defines a 7-day window between a key delete request and its permanent deletion, providing users with ample time to detect and rectify a cryptographic ransom attack against S3 instances.
Despite increasingly thorough security measures, researchers continue to find new ways to circumvent CSP controls.
Ransomware using cloud services for data exfiltration
Aside from ransomware targeting cloud services, threat actors are increasingly using cloud services to exfiltrate the data they intend to ransom. In September 2024, modePUSH reported that the BianLian and Rhysida ransomware groups are now using Azure Storage Explorer to exfiltrate data from victim environments. In October 2024, Trend Micro reported that a ransomware actor mimicking the notorious Lockbit ransomware group used samples that leverage Amazon’s S3 storage to exfiltrate data stolen from the targeted Windows or macOS systems.
SentinelLabs has identified a Python script that researchers call RansomES due to the Spanish language comments in the code. Designed to run on a Windows system, the script provides the actor with methods to exfiltrate the files to S3 or FTP and then encrypt the local versions.
Web application ransom attacks
Web applications are often run via cloud services. Their more minimal nature makes cloud environments a natural hosting point where the applications are easier to manage and require less configuration and upkeep than running on a full operating system. However, web applications themselves are vulnerable to extortion attacks.
SentinelLabs has identified several ransom scripts that target PHP applications. Researchers have identified a Python script called Pandora, which is a multi-tool targeting a variety of web services. This tool is unrelated to the Pandora ransomware group, which leverages binaries to target Windows systems.
Another PHP ransom script SentinelLabs has identified is attributed to the IndoSec group, an Indonesia-based threat actor. This script is a PHP backdoor that the attacker can use to manage and delete files, and perform ransom attacks.
Conclusion
Cloud ransom attacks are an emerging threat that organisations are better equipped to defend against now than in previous years, given the continuous dedication to CSP security measures in addition to a wealth of cloud security products designed to minimise risk.
SentinelLabs recommends the use of a Cloud Security Posture Management (CSPM) solution to discover and assess cloud environments and alert of issues such as misconfiguration and overly permissive storage buckets, as these are the primary flaws that facilitate the cloud ransom attack techniques described in this report. Additionally, always enforce good identity management practices, such as requiring MFA on all admin accounts and deploying runtime protection against all cloud workloads and resources.
