Full Report
A previously undocumented ransomware payload named NailaoLocker has been spotted in attacks targeting European healthcare organizations between June and October 2024. [...]
Analysis Summary
# Incident Report: NailaoLocker Ransomware Attack on EU Healthcare Organizations
## Executive Summary
European healthcare organizations were targeted by a novel ransomware strain dubbed NailaoLocker, deployed via an initial access technique involving DLL sideloading of a legitimate executable (`usysdiag.exe`). The attack resulted in file encryption using AES-256-CTR and the deployment of an unusually lengthy HTML ransom note, instructing victims to contact a specified ProtonMail address. The ultimate scope and intent remain somewhat ambiguous, with theories pointing toward a state-sponsored Chinese group possibly "moonlighting" for financial gain, though data exfiltration was not explicitly mentioned in the initial notes.
## Incident Details
- **Discovery Date:** Not explicitly stated, but investigation/reporting occurred around the time of the article's publication.
- **Incident Date:** Not explicitly stated.
- **Affected Organization:** EU Healthcare Organizations.
- **Sector:** Healthcare.
- **Geography:** Europe (EU).
## Timeline of Events
### Initial Access
- **Date/Time:** Unknown.
- **Vector:** DLL Sideloading using `sensapi.dll`.
- **Details:** Attackers leveraged the legitimate and signed executable `usysdiag.exe`. The malware loader (`NailaoLoader`) verified the environment via memory address checks before decrypting and loading the main payload (`usysdiag.exe.dat`) into memory.
### Lateral Movement
- Not explicitly detailed in the provided text, focus currently remains on initial execution and payload activation.
### Data Exfiltration/Impact
- **Impact:** File encryption of systems using AES-256-CTR scheme, appending the ".locked" extension to files.
- **Exfiltration:** Ransom note did not indicate data theft, which is unusual for modern ransomware operations.
### Detection & Response
- **Detection:** The activity was reported and analyzed by Orange CERT.
- **Response actions taken:** Not explicitly detailed, though analysis confirmed the presence and encryption mechanism.
## Attack Methodology
- **Initial Access:** DLL Sideloading (`sensapi.dll`) targeting a signed executable (`usysdiag.exe`).
- **Persistence:** Implied via the loading of the NailaoLoader.
- **Privilege Escalation:** Not explicitly detailed.
- **Defense Evasion:** Use of a legitimate, signed Windows executable (`usysdiag.exe`) combined with memory-only loading of the payload suggests evasion techniques.
- **Credential Access:** Not explicitly detailed.
- **Discovery:** Not explicitly detailed.
- **Lateral Movement:** Not explicitly detailed.
- **Collection:** Not explicitly detailed, though some thematic overlap with espionage tools was noted.
- **Exfiltration:** No direct evidence of exfiltration reported in ransom notes.
- **Impact:** File encryption utilizing AES-256-CTR, followed by the deployment of a highly specific ransom note.
## Impact Assessment
- **Financial:** Ransom demands likely involved financial negotiation (implied, but not quantified). One related US healthcare organization incident mentioned an $11M settlement.
- **Data Breach:** Unknown volume/type of data, but file encryption was confirmed.
- **Operational:** Significant operational disruption expected due to widespread file encryption.
- **Reputational:** Potential reputational damage linked to service interruption in the healthcare sector.
## Indicators of Compromise
- **Network indicators:** Contact email appeared to be: `johncollinsy@proton\[.\]me` (Defanged).
- **File indicators:** Encrypted file extension: `.locked`. Ransom note filename: "unlock\_please\_view\_this\_file\_unlock\_please\_view\_this\_file\_unlock\_please\_view\_this\_file\_unlock\_please\_view\_this\_file\_unlock\_please\_view\_this\_file\_unlock\_please\_view\_this\_file\_unlock\_please.html."
- **Behavioral indicators:** DLL Sideloading via `sensapi.dll` targeting `usysdiag.exe`. Memory decryption and loading of payload (`usysdiag.exe.dat`).
## Response Actions
- **Containment:** Not explicitly detailed (likely standard network segmentation and isolation of infected hosts).
- **Eradication:** Not explicitly detailed (likely deletion of malware components and recovery from backups).
- **Recovery:** Not explicitly detailed (likely decryption or system restoration).
## Lessons Learned
- The use of DLL hijacking targeting legitimate executables remains a persistent and effective initial access method.
- The ambiguity regarding data exfiltration requires organizations to assume double extortion tactics until proven otherwise, even if the note omits mention of stolen data.
- The complexity of attribution (potential state-sponsored actors engaging in ancillary financial crime) makes threat intelligence sharing critical.
## Recommendations
- Implement strict application control policies to restrict execution from unusual directories or processes.
- Harden monitoring for unusual processes loading DLLs, specifically monitoring legitimate binaries that exhibit suspicious behavior (e.g., Memory scanning/address checks).
- Conduct regular configuration audits to ensure signatures and hashes of critical system executables are monitored for tampering or unexpected execution paths.