Ransom.Win32.ASTROLOCKER.A represents a lesser-known but technically sophisticated ransomware strain with potential ties to the Mount Locker operation. First documented in March 2021, this Windows-targeted malware exhibits medium damage potential but has maintained relatively low distribution rates, accounting for just 2.1% of observed ransomware cases according to Sophos threat intelligence.
Infection Vectors and Operational Characteristics
ASTROLOCKER employs a dual infection methodology, typically arriving either as a secondary payload delivered by loader malware or through user-initiated downloads from compromised websites. Unlike many persistent threats, this ransomware follows a transient execution model – it performs its encryption routine then deliberately self-deletes to complicate forensic analysis.
Forensic investigators typically find artifacts in temporary directories (%TEMP%), ransom notes in multiple locations, and memory residues in Windows’ pagefile.sys. The malware demonstrates careful target selection, avoiding system-critical files and directories to maintain operational stability while maximizing impact on user data.
Technical Implementation and TTPs
Analysis reveals ASTROLOCKER shares significant Tactics, Techniques and Procedures (TTPs) with the Mount Locker ransomware group, including identical ransom note templates and service creation patterns. The malware creates services with random 16-character names and leverages %COMSPEC% for command execution, a hallmark of Mount Locker operations.
Sophos Managed Threat Response teams discovered during a 2021 investigation that ASTROLOCKER payloads were frequently hidden in C:\Users\Public\Music\ and executed via scheduled tasks named “updater”. These operational patterns strongly suggest either rebranding or affiliate relationships between the groups.
Detection and Mitigation Strategies
Security teams should implement multi-layered defenses against ASTROLOCKER, beginning with application whitelisting and restrictions on regsvr32.exe execution. Memory scanning with YARA rules proves particularly effective given the malware’s self-deletion behavior, as does monitoring for mass file operations and suspicious service creation.
Microsoft Defender’s Attack Surface Reduction rules provide additional protection when configured to block Office apps from creating child processes and prevent executable content execution from email. These controls help mitigate the initial infection vectors ASTROLOCKER commonly exploits.
Incident Response Considerations
When responding to suspected ASTROLOCKER infections, prioritize immediate system isolation and memory capture before shutdown. The malware’s connection to Mount Locker operations means responders should assume possible secondary payloads and conduct thorough hunting for associated persistence mechanisms.
Critical response steps include checking for recently created services with random names, examining scheduled tasks for “updater” entries, and scanning Public\Music directories for hidden executables. These indicators frequently surface in ASTROLOCKER compromise scenarios.
Strategic Implications for Security Teams
ASTROLOCKER’s emergence highlights the ransomware ecosystem’s fluid nature, where groups frequently rebrand or share infrastructure. Security leaders should incorporate these findings into threat models, particularly when investigating potential Mount Locker affiliate activity.
The strain’s technical profile offers valuable case studies for both defensive teams refining detection capabilities and red teams simulating realistic ransomware deployment patterns. Its operational characteristics bridge common ransomware tactics with distinctive elements like the self-deletion mechanism.
