BlueLocker Ransomware Resurfaces After Three-Year Dormancy, Breaches Pakistan Petroleum Limited

BlueLocker Ransomware Resurfaces After Three-Year Dormancy (TL-2026-2667), also tracked as Blue Locker, is a high-severity ransomware operation, first published 2026-09-26. It is attributed to Blue Locker ransomware operators with low confidence, affects Microsoft Windows (desktops, laptops, servers, and virtualized, maps to 13 MITRE ATT&CK techniques (T1012, T1057, T1070.006), and is covered by 9 detection rules and 19 indicators of compromise.

Key facts for TL-2026-2667

Threat ID
TL-2026-2667
Also known as
Blue Locker, BlueLocker, Bule Cryptor, Ransom:Win32/BlueLocker.MK!MTB
Severity
HIGH
Status
ACTIVE
Category
RANSOMWARE
First published
2026-09-26
Last reviewed
2026-09-26
Attribution
Blue Locker ransomware operators
Attribution confidence
LOW
Motivation
FINANCIAL
Target sectors
oil and gas, energy, government administration, critical infrastructure, technology
Target regions
pakistan, South Asia
Detection rules
9
Indicators of compromise
19

Malware and tooling in BlueLocker Ransomware Resurfaces After Three-Year Dormancy

Malware and tooling: BlueLocker (Blue Locker), Cipher, Limba, MemeCryptor, Shinra, Trust, proton, zola, MemeCryptor (github.com/DarkFunct/MemeCryptor)

BlueLocker (Blue Locker) ransomware, dormant since Microsoft's December 2021 signature addition, resurfaced in August 2025 with a confirmed attack on Pakistan Petroleum Limited (PPL) that encrypted servers/VMs, deleted backups via wmic SHADOWCOPY DELETE, and suspended PPL's financial operations for two days. Attribution is contested between an open-source MemeCryptor (Conti-inspired) codebase lineage identified by researcher rivitna and a Resecurity-assessed link to the Iranian-associated Proton ransomware family (Limba/Zola/Shinra/Cipher/Trust), with embedded Chinese-language strings assessed as a likely false flag.

How BlueLocker Ransomware Resurfaces After Three-Year Dormancy works

BlueLocker first appeared in the wild around November 2021; Microsoft added the detection signature Ransom:Win32/BlueLocker.MK!MTB on December 1, 2021, and the malware then went quiet for roughly three years. It resurfaced dramatically on August 6, 2025 with a confirmed breach of Pakistan Petroleum Limited (PPL), the country's second-largest oil and gas producer, responsible for roughly 20% of national natural gas supply. The operators encrypted servers and virtual machines, ran `wmic SHADOWCOPY DELETE` to destroy shadow-copy backups, and claimed to have exfiltrated approximately 1TB of data — including Petrel Studio exploration files, production databases, operations plans, financial records, and TMC data tied to the Sui and Adhi fields — though PPL publicly denied that sensitive data was compromised. The intrusion suspended PPL's financial operations and meter-reading capability for roughly two days.

Technically, two competing profiles exist. Researcher rivitna classifies the .blue/restore_file.txt artifacts as "BlueLocker (MemeCryptor)", tying them to an open-source, Conti-inspired ransomware project published on GitHub by user DarkFunct. That codebase implements multithreaded ChaCha20 file encryption, an XOR-obfuscated RSA public key used to wrap per-file symmetric keys, and BMP steganography to hide ChaCha20 keys inside meme images; it explicitly credits Conti for its multi-threading approach and its abuse of the Windows Restart Manager API to forcibly terminate processes (including Chrome.exe) that lock target files, such as Chrome's password database. Separately, Resecurity's reverse-engineering of acquired PPL-campaign binaries describes an AES+RSA hybrid scheme and assesses BlueLocker as a recent modification of the Proton ransomware family, which Israel's National Cyber Directorate (INCD) has linked to probable Iranian origins since 2023. Prior Proton-lineage strains cited as related include Limba (which has targeted Chinese victims), Zola, Shinra (detected April 2024, itself carrying suspicious Chinese-language strings such as "ZhuDongFangYu" and references to the Chinese AV vendor Qihoo 360), Cipher, and Trust. Analysts treat the Chinese-language artifacts as a probable false flag rather than evidence of Chinese origin, and note that Pakistan's stable diplomatic relations with both Iran and China make either direct-state explanation awkward, pointing instead to a third-party actor or reused/sold source code. Both explanations may be simultaneously true: Proton's source code has reportedly circulated for sale on the dark web, and MemeCryptor's codebase is public, so the same or different operators could be drawing on either or both lineages, or independently reusing the "Blue Locker" brand and ".blue" extension — a real risk given at least three unrelated malware families (Blue Locker/MemeCryptor, Proton/Shinra V2, and Phobos Blue) currently use ".blue"-style extensions.

Operationally, the malware persists via a Registry Run key (`HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Run`), bypasses UAC through registry manipulation, uses XOR-encoded strings (including Chinese-character encodings of process names such as "Chrome.exe") to frustrate static analysis, performs timestomping and virtualization/sandbox checks, and enumerates the registry, running processes, and the file system before encrypting. It avoids OS-critical paths (Windows, System32, ProgramFiles, System Volume Information, Boot) and skips certain extensions (.cat, .bat, .cmd, .ps1, .vbs) to keep the machine bootable enough to display the ransom note, dropped as `restore_file.txt` (and, per some reporting, `HOW_TO_BACK_FILES.html`). The note is headed "[ Hello! ]", signed "BY BLUE LOCKER", threatens to "report the hack to mainstream media and release your data to social media and competitors", gives no fixed ransom figure, and directs victims to a ProtonMail address and an XMPP/Jabber contact (with a Tox ID also referenced); the group deliberately runs no dedicated Tor leak site. Distribution is via phishing emails with malicious attachments, trojanized downloads, unsecured file-sharing platforms, and compromised websites, with capability to propagate across networks, removable storage, cloud environments, and network-attached storage.

In response, Pakistan's National Cyber Emergency Response Team (NCERT) issued advisory NCA-38.081025 ("Critical Global Ransomware Threat: Blue Locker & Shinra Campaign") on August 10-11, 2025 to 39 government ministries and institutions — including Cabinet, Interior, Foreign Affairs, the Election Commission, the National Assembly, and the FBR — rating the threat "extremely high" severity and confirming its own systems were "detecting and blocking it continuously". No CVE or exploited vulnerability underlies this campaign; initial access is social-engineering-driven, not exploit-driven.

MITRE ATT&CK techniques used in TL-2026-2667

Discovery

T1012 Query Registry; T1057 Process Discovery

Defense Evasion

T1070.006 Timestomp; T1140 Deobfuscate/Decode Files or Information; T1497 Virtualization/Sandbox Evasion

Execution

T1204.002 Malicious File

Impact

T1489 Service Stop; T1490 Inhibit System Recovery

Persistence

T1547.001 Registry Run Keys / Startup Folder

Privilege Escalation

T1548.002 Bypass User Account Control

Credential Access

T1555.003 Credentials from Web Browsers

Initial Access

T1566.001 Spearphishing Attachment

defense-impairment

T1685 Disable or Modify Tools

Affected products and versions in BlueLocker Ransomware Resurfaces After Three-Year Dormancy

  • Microsoft — Windows (desktops, laptops, servers, and virtualized environments)
    Vulnerable versions: all Windows versions lacking adequate EDR and offline-backup isolation
  • N/A — Network-attached storage (NAS) and cloud backup infrastructure
    Vulnerable versions: any internet-reachable or non-isolated backup/NAS systems

Remediation for BlueLocker Ransomware Resurfaces After Three-Year Dormancy

Immediate actions

  • Isolate and take offline all backup and NAS systems immediately upon suspected compromise to prevent wmic SHADOWCOPY DELETE-style backup destruction
  • Block the ransom-note communication channels (ProtonMail and XMPP/Jabber addresses) at email and network gateways and hunt for prior contact with them
  • Hunt across endpoints for the mutex artifact `wbizecif48njqgpprzkm6769`, the ransom note filename `restore_file.txt`, and the `.blue` file extension

Workarounds

  • Restrict and monitor use of wmic.exe and vssadmin.exe on servers to detect and block shadow-copy deletion attempts
  • Enforce network segmentation between IT and OT/financial systems to limit encryption blast radius in oil & gas operational environments
  • Apply strict email attachment filtering and user-execution controls given the phishing/trojanized-download delivery vector

Longer-term hardening

  • Deploy EDR with behavioral detection tuned to Registry Run-key persistence, UAC-bypass activity, Restart-Manager-style forced process termination, and mass file-rename/encryption patterns
  • Enforce offline, immutable, air-gapped backups for critical-infrastructure and OT-adjacent environments so shadow-copy deletion cannot eliminate recovery options
  • Reduce reliance on browser-stored credentials (harden or migrate off Chrome's local password store) given the malware's demonstrated targeting of browser password databases

Timeline of BlueLocker Ransomware Resurfaces After Three-Year Dormancy

  • BlueLocker ransomware first observed in the wild, per Microsoft telemetry and later researcher retrospectives.
  • Microsoft Defender adds the detection signature Ransom:Win32/BlueLocker.MK!MTB to its threat encyclopedia.
  • The Proton ransomware family - later assessed by Resecurity as sharing lineage with Blue Locker - is first observed operating, with probable Iranian origins per Israel's INCD.
  • Shinra, a Proton-family variant carrying suspicious Chinese-language strings such as 'ZhuDongFangYu', is detected; NCERT later frames the August 2025 campaign as a joint 'Blue Locker & Shinra' threat.
  • Israel's National Cyber Directorate (INCD) publishes its Shinra Malware Profile, assessing probable Iranian origins for the Proton lineage.
  • Blue Locker operators breach Pakistan Petroleum Limited (PPL), encrypting servers and virtual machines, deleting backups via wmic SHADOWCOPY DELETE, and suspending PPL's financial operations for roughly two days; operators claim ~1TB of exfiltrated data including Petrel Studio exploration files and TMC data from the Sui and Adhi fields.
  • Threat-intel monitoring accounts publicly flag the PPL breach and its two-day operational impact.
  • Pakistan's National Cyber Emergency Response Team (NCERT) issues advisory NCA-38.081025 ('Critical Global Ransomware Threat: Blue Locker & Shinra Campaign') to 39 government ministries and institutions.
  • Resecurity publishes a reverse-engineering analysis of acquired Blue Locker binary samples, assessing links to the Proton ransomware family (Limba, Zola, Shinra, Cipher, Trust) and flagging embedded Chinese-language strings as a likely false flag.
  • SOCRadar publishes a 'Dark Web Profile' retrospective on Blue Locker, citing researcher rivitna's classification of the .blue/restore_file.txt artifacts as 'BlueLocker (MemeCryptor)' tied to the open-source DarkFunct/MemeCryptor GitHub project.

Sources cited for BlueLocker Ransomware Resurfaces After Three-Year Dormancy

More in ransomware

Detection coverage for TL-2026-2667

As of 2026-09-26, Threadlinqs Intelligence publishes 9 detection rule(s) for TL-2026-2667 across Splunk SPL, Microsoft KQL and Sigma, covering 19 indicator(s) of compromise. The whole corpus is readable without an account; a free account unlocks full detection query text in Splunk SPL, Microsoft KQL and Sigma; paid tiers add raw indicator values, correlation and the MCP server. Threadlinqs MCP server · View plans.

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