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Researchers found that Rook is a 64-bit Windows ransomware family built heavily from the leaked Babuk source code, reusing routines for service and process termination, shadow copy deletion, and core encryption logic while adding a more efficient multithreaded file-encryption model. The malware encrypts files with per-file AES keys protected by RSA-2048 through the Mbed TLS library, appends the .Rook or .ROOK extension, drops a ransom note named HowToRestoreYourFiles.txt, and targets local drives, mounted volumes, network resources, and operator-supplied paths. Analysts also observed Rook deleting volume shadow copies, attempting to stop backup, database, and security tools, storing victim key material in the Windows registry, hiding its executable in an NTFS alternate data stream named :ask, and deleting itself after execution without observed persistence.
Threat intelligence linked Rook’s early operations to data-theft extortion claims, including a reported first victim in Kazakhstan’s financial sector, where the operators said they stole 1,123 GB of data. Delivery has been associated mainly with third-party access frameworks such as Cobalt Strike, though phishing has also been reported, and samples have appeared packed with UPX or VMProtect. Separate reverse-engineering work concluded that NightSky is very likely a fork of Rook, sharing nearly identical key generation, threading, synchronization, encrypted file structure, and RSA/AES workflow, with the main cryptographic change being NightSky’s use of AES-128-CBC instead of Rook’s intermittent AES-128-ECB approach.
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By November 30, Rook had claimed its first victim, identified as a Kazakh financial institution. The operators said they had stolen 1,123 GB of data from the victim, indicating a dual-extortion operation.
SentinelOne reported that researcher Zack Allen first noticed the Rook ransomware family on VirusTotal on November 26. This marks the earliest explicit sighting of the malware in the provided references.
A GitHub reverse-engineering report concluded that NightSky ransomware is very likely a fork of Rook based on extensive code similarity in cryptography, threading, synchronization, and encrypted file structure. The report said the overlap could indicate either the same threat actor or access to leaked source code.
A reverse-engineering analysis detailed ROOK's hybrid AES and RSA-2048 encryption, registry-stored victim key material, alternate data stream self-hiding, and multithreaded traversal. The analysis also concluded that ROOK reused multiple components from the leaked Babuk source code while improving parts of the threading model.
SentinelOne published research describing Rook's behavior, delivery methods, dual-extortion model, and technical overlap with the leaked Babuk codebase. The report assessed that Rook was likely built opportunistically from leaked Babuk source code.
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Researchers detailed **BlueSky**, an emerging Windows ransomware family that rapidly encrypts files through a multithreaded design and uses anti-analysis features plus a staged PowerShell infection chain. The malware was observed being delivered from `kmsauto[.]us` via `start.ps1` and `stage.ps1`, then saved locally as `javaw.exe`. It attempts privilege escalation with **JuicyPotato** on older Windows systems and uses exploits for `CVE-2020-0796` and `CVE-2021-1732` on newer hosts before encrypting files, appending the `.bluesky` extension, and dropping ransom notes named `# DECRYPT FILES BLUESKY #.txt` and `# DECRYPT FILES BLUESKY #.html`. Technical analysis found BlueSky shares strong code similarities with **Conti v3**, particularly in its multithreaded architecture and network share enumeration, while its cryptography aligns more closely with **Babuk** through the use of **ChaCha20** for file encryption and **Curve25519** for key generation. The ransomware excludes selected extensions and directories, creates host-specific identifiers, and stores encryption-state artifacts including a mutex and `HKCU\Software\<32-byte ID>` registry entries. Investigators also found **RedLine**-related samples hosted on the same domain, indicating possible infrastructure overlap or operational ties even though no direct code overlap was identified.
Aug 14, 2026
Attackers brute-forced the `sa` account on an internet-facing Microsoft SQL Server and escalated a compromise into a full BlueSky ransomware deployment in about 32 minutes. After access was obtained, they enabled `xp_cmdshell`, launched PowerShell payloads, established a Cobalt Strike beacon, and used Tor2Mine tooling to disable antivirus, create persistence, and install an XMRig-based Monero miner. The intrusion then expanded through remote service creation and SMB activity toward domain controllers and file shares before the ransomware binary, masquerading as `vmware.exe`, was executed on the initial host. Files were encrypted with the `.bluesky` extension and a ransom note named `# DECRYPT FILES BLUESKY #.txt` was dropped, while investigators reported no evidence of data exfiltration. BlueSky is a Windows-focused ransomware family observed since 2022 that has been distributed through phishing emails, phishing sites, and trojanized downloads in addition to direct server compromise. Technical analysis shows the malware adjusts privileges, hides threads from debuggers, creates a mutex, and selectively skips some system-related files and directories while targeting user and database data. It accelerates encryption across local and network resources using multithreading and Windows I/O completion ports, stores recovery-related data in the Windows registry, terminates selected processes before encryption, appends the `.bluesky` extension to locked files, and generates ransom notes in both TXT and HTML formats.
Aug 14, 2026
Researchers reported that multiple ransomware families, including **DoNex**, **BabLock/Rorschach**, and **LockBit Black (v3)**, share substantial code and operational overlap with **LockBit**, underscoring how leaked builder code and recycled components continue to fuel new strains. SANS assessed DoNex as an unoriginal **LockBit-derived** operation closely resembling **Darkrace**, with behavior including process and service termination, network-share enumeration, event-log clearing, ransom-note deployment, and forced reboot after encryption. Trend Micro similarly found that BabLock appears heavily based on **LockBit 2.0** while incorporating features from other families, using DLL sideloading, Direct SysCalls, VMProtect, and unusual random numeric file extensions. Separate reverse engineering of LockBit v3 identified serious implementation flaws, including a **keystream reuse** bug and a design issue that could cause permanent data corruption, enabling partial decryption in some cases via an open-source decryptor. Operational reporting also showed LockBit affiliates continuing to refine delivery and post-exploitation methods. ASEC documented phishing emails posing as copyright claims that delivered LockBit through nested password-protected archives and a fake PDF executable, after which the malware deleted shadow copies, altered boot recovery settings, established persistence, and encrypted files with the `.lockbit` extension. SentinelOne described a LockBit-linked intrusion that began with **Log4Shell** exploitation against an unpatched **VMware Horizon** server and progressed to abuse of legitimate Microsoft Defender tooling for DLL sideloading of **Cobalt Strike**, alongside PowerShell execution, web-shell deployment, and other living-off-the-land techniques. Together with earlier DarkSide analysis showing similar use of **Salsa20/RSA**, service killing, shadow-copy deletion, and network-resource encryption, the reports show a ransomware ecosystem in which LockBit code, cryptography, and tradecraft are repeatedly repackaged into new campaigns and variants.
Aug 15, 2026