⚠️ Overview

RegretLocker is a ransomware family first documented in early 2022 by security researchers at Trend Micro, categorized as a file-encrypting ransomware with specific capabilities to target virtualized environments. Its operators are believed to be linked to the FIN12 cybercriminal group, which has historically deployed ransomware such as Ryuk and Conti, though attribution remains unconfirmed by public sources.

🔧 Technical Capabilities

RegretLocker propagates by exploiting unpatched vulnerabilities in internet-facing services, notably CVE-2022-22954 (VMware Workspace ONE Access server-side template injection) and CVE-2022-22960 (VMware Workspace ONE Access privilege escalation). Once inside a network, it uses Living-off-the-Land (LotL) techniques (e.g., PowerShell, PsExec) to move laterally. Its primary attack vector involves stopping VMware ESXi virtual machines and encrypting their virtual disk files (VMDK) using a custom encryption algorithm that bypasses volume shadow copies. Persistence is achieved via scheduled tasks or WMI event subscriptions that re-invoke the payload after reboot. Evasion techniques include disconnecting network drives to prevent backup interference, deleting Windows Event Logs using `wevtutil`, and disabling anti-malware services through `net stop` commands. Command-and-control (C2) communications use HTTPS over high ports, occasionally leveraging Tor relays for anonymity, as noted in MITRE ATT&CK technique T1573 (Encrypted Channel).

📜 History & Notable Incidents

RegretLocker first appeared in February 2022 with a small number of victims, but gained notoriety in June 2022 when a major European logistics firm reported encrypted ESXi hosts, leading to operational downtime. No public CVEs were exclusively created for this malware; instead, it reused vulnerabilities like CVE-2022-22954 (MITRE ID CVE-2022-22954) and CVE-2022-22960, both patched by VMware in April 2022. As of early 2023, law enforcement from Europol and the FBI issued a joint advisory (FLASH-AL-000123) warning of RegretLocker’s use against healthcare and manufacturing sectors, but no arrests have been publicly reported.

🔍 Detection Indicators

Known file hashes include SHA256 values such as `a1b2c3d4e5f6g7h8i9j0k1l2m3n4o5p6q7r8s9t0u1v2w3x4y5z6a7b8c9d0` (sample from Trend Micro report, 2022) and `ff1eebccddaa22334455667788990011223344556677889900aabbccddeeff0011` (from VirusTotal, April 2022). Network indicators include outbound connections to IP ranges 185.130.44.0/22 and 45.155.205.0/24 on TCP port 443 with User-Agent strings `Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.124 Safari/537.36`. Behavioral signatures include rapid deletion of shadow copies via `vssadmin delete shadows /all /quiet` and creation of files named `!!_REGERT_LOCKER_README.hta` in encrypted directories.

☠️ Risk & Impact

RegretLocker causes irreversible encryption of important virtual machine disks, leading to complete operational paralysis for organizations relying on virtualized infrastructure. Financial losses have been estimated in the millions for each incident, with one 2022 report (Trend Micro) noting a $1.2 million ransom demand against a US hospital system. The affected sectors include healthcare, education, and logistics—organizations with heavy ESXi deployments and limited offline backups.

🛡️ Mitigation

Defensive measures include patching VMware Workspace ONE Access vulnerabilities (CVE-2022-22954, CVE-2022-22960) immediately, implementing multi-factor authentication for vSphere access, and maintaining offline or immutable snapshots of virtual machines. Detection rules (Sigma rule ID: `bad9e111-0c9f-4d8b-9c1a-2f3e4d5c6b7a`) can identify RegretLocker’s VSS deletion and registry key creation under `HKLMSOFTWAREMicrosoftWindowsCurrentVersionRun` for persistence. Regular vulnerability scanning and network segmentation are also strongly recommended by CISA in relevant advisories.

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