BlueSky Ransomware: Analysis, Detection, and Recovery

BlueSky Ransomware: A Comprehensive Analysis of the Emerging Cyber Threat

Ransomware has become one of the most formidable challenges in the realm of cybersecurity, with BlueSky Ransomware representing the latest evolution of these malicious attacks. Emerging in July 2022, BlueSky has quickly gained notoriety for its rapid encryption capabilities and sophisticated evasion techniques.

This article delves into the intricacies of BlueSky Ransomware, exploring its technical mechanisms, attack methodologies, and the broader implications for cybersecurity.

BlueSky Ransomware Profile

BlueSky Ransomware burst onto the scene as a malicious software that leverages trojanized downloads from dubious websites to infiltrate systems. Unlike other ransomware operations, BlueSky eschews the practice of maintaining a victim data listing blog, opting for a more covert approach. It indiscriminately targets entities ranging from large enterprises and high-value targets to small and medium-sized businesses (SMBs), showing no preference for the size or type of its victims.

Technical Analysis of BlueSky Ransomware

Infection and Operation

The distribution of BlueSky Ransomware is primarily through compromised downloads, or through sophisticated third-party frameworks such as Cobalt Strike and BRc4. Notably, it employs the NtSetInformationThread function, a technique documented by Microsoft, to hide threads from debuggers and Endpoint Detection and Response (EDR) tools, effectively evading analysis.

To spread within a network, BlueSky identifies local drives using the GetLogicalDriveStringsW API and disseminates via the Server Message Block (SMB) protocol, a common vector for lateral movement. Upon infection, victims are directed to a ‘DECRYPTOR’ portal where they can manage their recovery process, highlighting the ransomware’s user-centric design.

Encryption Algorithms

In terms of encryption, BlueSky utilizes the ChaCha20 algorithm for file encryption, a method known for its speed and security. For key generation, it employs Curve25519, an elliptic curve offering high security levels. These choices underscore the ransomware’s focus on fast and secure encryption, traits that have drawn comparisons with infamous groups like Conti and Babuk.

Dropper Mechanism

The initial delivery of BlueSky is often through a PowerShell script named start.ps1, which is fetched from a fake website. This script is obscured using Base64 encoding and DEFLATE compression, demonstrating the ransomware’s multi-layered obfuscation techniques. Once on the victim’s machine, the payload masquerades as javaw.exe, a tactic to mimic legitimate applications and avoid detection.

Privilege Escalation

BlueSky attempts to escalate privileges using vulnerabilities such as CVE-2020-0796 and CVE-2021-1732, depending on the Windows version in use. These exploits are indicative of the ransomware’s adaptability and its creators’ technical acumen.

Ransomware Payload

The payload, once downloaded, is saved and executed from the Startup folder, ensuring its persistence across system reboots. Following file encryption, BlueSky drops a ransom note in both text and HTML formats, providing victims with instructions on how to proceed with the ransom payment.

Anti-Analysis Techniques

BlueSky is designed to be a tough nut to crack for security analysts, employing string encryption, API obfuscation, and anti-debugging measures. These anti-analysis techniques complicate efforts to dissect and understand the ransomware’s inner workings.

Unique ID Generation

Each victim of BlueSky is assigned a unique user ID, generated based on system information. This ID is used to track the victim and manage the decryption process. The ransomware also creates a registry key to store encryption-related data, further entrenching itself within the infected system.

File Encryption Process

BlueSky is selective in its encryption process, sparing certain file extensions and directory names. It uses a multithreaded queue system to encrypt files, showcasing its efficiency and the threat it poses to organizations’ data integrity.

Association with RedLine Infostealer

Interestingly, some samples of BlueSky were found on the same domain as the RedLine infostealer. However, no direct code overlap was observed, suggesting a possible but not definitive association between the two threats.

Indicators of Compromise (IOCs) and Detections

Security teams can stay vigilant for BlueSky attacks by monitoring for IOCs such as SHA256 hashes of the ransomware payloads, obfuscated PowerShell downloaders, and exploits used for privilege escalation. URLs related to the ransomware’s command and control servers and ransom note are also critical for detection.

Attack Methodology

Initial Breach

BlueSky Ransomware’s attack cycle often begins with a brute force attack on public-facing MSSQL servers. This method was detailed in a report by The DFIR Report, where attackers made over 10,000 failed attempts on the “sa” (System Administrator) account before gaining access. Once inside, they leveraged the “xp_cmdshell” to execute shell commands, further solidifying their foothold within the system.

Post-Exploitation Actions

Following the initial breach, attackers establish a Cobalt Strike connection and execute PowerShell scripts to perform SMB scans and discover additional network resources. This phase also includes connecting to a Tor2Mine server and executing scripts to disable antivirus software, drop miner payloads, and maintain persistence within the compromised environment. Lateral movement is a key component of the BlueSky attack, with the ransomware moving toward domain controllers and file shares to maximize its impact.

Mitigation and Prevention Strategies

Detection and Response

The SentinelOne Singularity XDR Platform is equipped to detect and prevent BlueSky ransomware behaviors and artifacts. For organizations not equipped with this platform, Palo Alto Networks offers protections against BlueSky through a suite of services including Cortex XDR, Next-Generation Firewall, Advanced URL Filtering, DNS Security, and WildFire.

Best Practices

Organizations can mitigate the risk of a BlueSky ransomware attack by implementing several best practices, including:

  • Regular security audits to identify vulnerabilities.
  • Training employees to recognize and respond to cybersecurity threats.
  • Using strong, unique passwords and updating them regularly.
  • Enabling multi-factor authentication (MFA) for all user accounts.
  • Keeping systems up to date with the latest patches and updates.
  • Implementing a robust backup and disaster recovery plan to minimize data loss in the event of an attack.

Cryptocurrency and Ransomware

Ransomware operations like BlueSky typically demand payment in cryptocurrencies due to the perceived anonymity and difficulty in tracing transactions. This preference for cryptocurrencies poses significant challenges for cybersecurity professionals and financial regulators alike, as it facilitates cross-border transactions without the need for centralized authority, making it the preferred method for cybercriminals to receive ransoms.

Case Studies and Real-World Incidents

One notable incident involving BlueSky ransomware was the brute-force attack on an MSSQL Server that led to the rapid deployment of the ransomware across the network. The attack was executed within an hour of initial access, and the intrusion lasted approximately 30 minutes with no data exfiltration observed. This case study underscores the speed and efficiency of BlueSky ransomware attacks and the importance of swift incident response.

Combating BlueSky Ransomware

For organizations looking to combat the BlueSky Ransomware threat, advanced threat hunting techniques are essential. Cyborg Security’s HUNTER Platform provides hunt packages designed to counteract threats like BlueSky. These packages include behavioral threat hunting content that can be instrumental in detecting and mitigating ransomware attacks.


BlueSky Ransomware represents a significant and evolving threat to organizations worldwide. Its sophisticated encryption methods, evasion techniques, and rapid propagation make it a formidable challenge for cybersecurity teams. By understanding the ransomware’s mechanisms, staying vigilant for IOCs, and employing robust mitigation strategies, organizations can better protect themselves against this and other ransomware threats.

As the landscape of cyber threats continues to evolve, proactive defense measures and advanced threat hunting will remain critical components in the fight against ransomware.