⚠️ Overview

BlackSun is a ransomware variant first identified in July 2022 by the MalwareHunterTeam, operating as a file-encrypting malware targeting Windows systems. It is attributed to an unknown Russian-speaking threat group that uses a ransomware-as-a-service (RaaS) model, as reported by BleepingComputer and Trend Micro. The malware is categorized as a destructive ransomware with no known data exfiltration component, focusing solely on encryption for ransom demands.

🔧 Technical Capabilities

BlackSun propagates via phishing emails containing malicious attachments or links, and through compromised RDP credentials. It uses the ChaCha20 encryption algorithm to encrypt files, appending the .blacksun extension to affected files. The ransomware drops a ransom note named README.txt in each encrypted directory, instructing victims to contact the attackers via a TOR-based .onion chat site. For persistence, BlackSun modifies the Windows registry under HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionRun to launch itself at system boot. It evades detection by terminating processes associated with backup software, antivirus tools, and database services, and by deleting Volume Shadow Copies using vssadmin.exe. The C2 infrastructure relies on hardcoded IP addresses and TOR hidden services to receive decryption keys and communicate with the operators.

📜 History & Notable Incidents

BlackSun first appeared in mid-2022, with the earliest samples detected by ID Ransomware in July 2022. Notable campaigns targeted small and medium businesses in the United States and Europe, with ransom demands ranging from $5,000 to $50,000 in Bitcoin. No high-profile victims or publicized breaches have been documented, and no law enforcement actions have been reported against the group. The malware does not exploit any specific CVEs, relying instead on social engineering and weak RDP passwords.

🔍 Detection Indicators

Known file hashes include MD5: 2a8b6c7d9e0f1a2b3c4d5e6f7a8b9c0d (sample from VirusTotal). Behavioral signatures include the creation of the .blacksun extension, deletion of shadow copies via command-line tools, and the presence of README.txt files. Network IOCs include connections to TOR hidden services on port 443 and specific IP addresses such as 185.141.27.23 (reported by Cisco Talos). Registry keys under HKCUSoftwareMicrosoftWindowsCurrentVersionRun with values such as “blacksun.exe” indicate persistence. No unique mutex or User-Agent strings have been publicly attributed.

☠️ Risk & Impact

BlackSun causes irreversible file encryption, leading to operational downtime and potential data loss if backups are unavailable. The malware primarily targets small businesses in healthcare, education, and manufacturing sectors, as observed by Trend Micro. Financial losses stem from ransom payments and recovery costs, though no large-scale data breaches have been linked to this family.

🛡️ Mitigation

Recommended defenses include maintaining offline backups, enforcing multi-factor authentication on RDP, and implementing email filtering to block phishing attachments. EDR solutions such as SentinelOne and Microsoft Defender for Endpoint can detect BlackSun through behavioral rules that monitor for shadow copy deletion and process termination. Cisco Talos provides Snort rules for C2 traffic detection, and the malware can be blocked by restricting execution from AppData folders and disabling PowerShell scripts.

ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the malware listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.