BlueSky Ransomware: In-Depth Analysis, Detection, and Mitigation

What is BlueSky Ransomware?

BlueSky ransomware emerged in July 2022 and is known to distribute their payload through trojanized downloads from risky websites. Based on current observations, BlueSky operators currently do not operate a victim data listing blog.

What Does BlueSky Ransomware Target?

BlueSky ransomware is known to target large enterprises and high-value targets as well as small and medium-sized businesses (SMBs).

How Does BlueSky Ransomware Work?

BlueSkyThanos ransomware targets its victims through trojanized downloads.  Once active, the ransomware has the ability to move laterally (spreading via SMB).

BlueSky Ransomware Technical Details

Initial delivery can vary by affiliate. However, some observed mechanisms include delivery via third-party framework (aka Cobalt Strike & BRc4) or delivery via trojanized download. One particular instance of this type was recently documented by researchers at CloudSEK. Trojanized downloads of the BlueSky ransomware were briefly made available via a website known to host questionable executables to begin with such as application “cracks” and “keygens”.

BlueSky payloads attempt to hide, or evade, debuggers (a form of analysis evasion) by way of NtSetInformationThread. The NtSetInformationThread function is utilized to hide threads launched by the malware executable. This prevents certain events from being viewed or hooked by various analysis methods such as debuggers or EDR. In this specific case, “ThreadInformationClass=0x11” can be ‘roughly translated’ to ThreadInformationClass=ThreatHideFromDebugger. Local drives are discovered and stored via GetLogicalDriveStringsW, and the ransomware will traverse each local, logical drive serially.

BlueSky is able to spread laterally across accessible networks by way of SMB ( Server Message Block).

When infected, victims are instructed to visit the BlueSky ‘DECRYPTOR’ portal. At that point, they are able to enter their unique recovery ID, allowing them to contact their attacker, test decryption, and fully manage their ‘recovery’. The BlueSky portal boldly lists the impending time limit, and the increasing dollar amounts required to regain access to their data.

How to Detect BlueSky Ransomware

The SentinelOne Singularity XDR Platform detects and prevents malicious behaviors and artifacts associated with BlueSky ransomware.

If you do not have SentinelOne deployed, here are a few ways you can identify BlueSky ransomware in your network:

Security Tools

Use anti-malware software or other security tools capable of detecting and blocking known ransomware variants. These tools may use signatures, heuristics, or machine learning algorithms, to identify and block suspicious files or activities.

Network Traffic

Monitor network traffic and look for indicators of compromise, such as unusual network traffic patterns or communication with known command-and-control servers.

Security Audits

Conduct regular security audits and assessments to identify network and system vulnerabilities and ensure that all security controls are in place and functioning properly.

Education & Training

Educate and train employees on cybersecurity best practices, including identifying and reporting suspicious emails or other threats.

Backup & Recovery Plan

Implement a robust backup and recovery plan to ensure that the organization has a copy of its data and can restore it in case of an attack.

How to Mitigate BlueSky Ransomware

SentinelOne Singularity XDR Platform prevents BlueSky ransomware infections. In case of an infection, the SentinelOne Singularity XDR Platform detects and prevents malicious behaviors and artifacts associated with BlueSky ransomware.

SentinelOne customers are protected from BlueSky ransomware without any need to update or take action. In cases where the policy was set to Detect Only and a device became infected, remove the infection by using SentinelOne’s unique rollback capability. As the accompanying video shows,  the rollback will revert any malicious impact on the device and restore encrypted files to their original state.

In case you do not have SentinelOne deployed, there are several steps that organizations can take to mitigate the risk of BlueSky ransomware attacks:

Educate employees

Employees should be educated on the risks of ransomware, and how to identify and avoid phishing emails, malicious attachments, and other threats. They should be encouraged to report suspicious emails or attachments, and to avoid opening them, or clicking on links or buttons in them.

Implement strong passwords

Organizations should implement strong, unique passwords for all user accounts, and should regularly update and rotate these passwords. Passwords should be at least 8 characters long and should include a combination of uppercase and lowercase letters, numbers, and special characters.

Enable multi-factor authentication

Organizations should enable multi-factor authentication (MFA) for all user accounts, to provide an additional layer of security. This can be done through the use of mobile apps, such as Google Authenticator or Microsoft Authenticator, or the use of physical tokens or smart cards.

Update and patch systems

Organizations should regularly update and patch their systems, to fix any known vulnerabilities, and to prevent attackers from exploiting them. This includes updating the operating system, applications, and firmware on all devices, as well as disabling any unnecessary or unused services or protocols.

Implement backup and disaster recovery

Organizations should implement regular backup and disaster recovery (BDR) processes, to ensure that they can recover from ransomware attacks or other disasters. This includes creating regular backups of all data and systems and storing these backups in a secure, offsite location. The backups should be tested regularly to ensure that they are working and that they can be restored quickly and easily.