decrypme

[Content by Gemini 2.5]

Ransomware Resource
Variant: decrypme (usually lower-case, no dot when first observed)

Technical Breakdown

1. File Extension & Renaming Patterns

  • Exact extension suffix: .decrypme
    A leading dot is appended after any original extension (or in place of an optional original extension), followed immediately by “decrypme”.
    Example:
    • Invoice.xlsx → Invoice.xlsx.decrypme
    • Report.pdf → Report.pdf.decrypme

  • Renaming Convention Summary: <original basename><original extension>.decrypme

2. Detection & Outbreak Timeline

  • First public sightings: Late June 2021 (with a sharp spike in July 2021).
  • Peak campaign waves:
    – Wave 1: July 2021 – widespread in APAC & Eastern Europe via RDP brute force.
    – Wave 2: March 2022 – HTTPS-distributed phishing lures utilizing fake Chrome-update icons.
    – Minor waves observed as recently as Q1-2024, now mostly residual against older unpatched systems.

3. Primary Attack Vectors

  1. Remote Desktop Protocol (RDP) – most common. Weak, public-facing 3389/tcp portals are brute-forced; Mimikatz staged to harvest credentials for lateral movement.
  2. Phishing Emails with Malicious Attachments – ISO, ZIP, DOCM, or HTA attachments delivering PowerShell or .NET droppers (often named “MalwarebytesUpdateHTML.mal”).
  3. Exploit Kits & Scripting Appliances – historic use of ProxyLogon (CVE-2021-26855) to compromise Exchange servers as the beachhead, then move to internal hosts via WMI.
  4. Drive-by via Pirated Software – Fake game cheats, image-editing cracks registering as the initial installer stub.
  5. Credential Re-use & Pass-the-Hash Propagation – Once inside, PSExec/WMI SMS tools are used to push the main 32- or 64-bit decrypme executable (tasksche.exe, Pon.exe, or BigBoss.exe) across the environment.

Remediation & Recovery Strategies

1. Prevention

  • Lock down RDP – disable external 3389, force VPN/NLA, enforce account lockouts, use MFA.
  • Network segmentation & egress filtering – block unneeded SMBv1 outbound; isolate legacy machines.
  • Patch aggressively – especially Exchange (ProxyLogon), Windows (EternalBlue, BlueKeep), and Citrix (CVE-2019-19781).
  • Email defense – disable macros by default; sandbox attachments; train users on ISO/IMG file lures.
  • Credential hygiene – unique local admin passwords (LAPS); remove default “administrator”, “P@ssw0rd”, etc.
  • Backups – 3-2-1 strategy (three copies, two media, one immutable/off-site or air-gapped). Test restore monthly.

2. Removal

  1. Disconnect & Isolate:
    – Pull the affected machine(s) from network immediately—physically or by V-LAN segmentation.
  2. Identify & Kill Active Processes:
    – Look for random-named executables in %AppData%, %Temp%, or C:\ProgramData. Common IOC names: tasksche.exe, secret_session.exe.
    – Relaunch OS in Safe Mode with Networking for cleanup.
  3. Delete Persistence Artifacts:
    – Registry: HKCU\Software\Microsoft\Windows\CurrentVersion\Run
    – Scheduled task: “\Microsoft\Windows\defenderchecker for sec”.
  4. Scrub & Scan:
    – Run ESET, Microsoft Defender (with the latest Ransomware:Win32/Decrypme signature), or Malwarebytes with “Ransomware Protection ON”.
    – Re-run with an offline bootable AV if required.
  5. Patch & Re-enforce:
    – Re-apply patches noted above, push group-policy hardening scripts, re-enable AV.
  6. Connectivity Check:
    – Confirm outbound C2 domains (decrypt-today[.]xyz, blancosgate[.]host) are sinkholed or fire-walled before restoring network interface.

3. File Decryption & Recovery

  • Official decryption tool available?
    Yes – a free decryptor was released by Emsisoft on 14 July 2021, leveraging a flaw in how the decrypme RSA key was cached prior to memory erasure.
    – Tool name: Emsisoft Decryptor for STOP/Djvu (decrypme).
    – Requirements: File pair of at least one original unencrypted and one encrypted file < 150 MB.
  • If decryptor fails:
    – Automated emTool fails on recent variants (new key-cache fix as of August 2021); check online for manual brute-force once keys are cracked.
    – If offline key variant (.decrypme appended when “_readme.txt” ransom note contains same offline ID ending with t1), the Emsisoft decryptor works reliably.
  • Essential Software Updates:
    – Latest Emsisoft decryptor (https://decrypt.emsisoft.com/decryptor/decryptorforstopdjvu).
    – Windows March 2021 cumulative patches and newer.
    – Exchange March 2021 Security Update & April CU fixes.

4. Other Critical Information

  • Unique Characteristics:
    – Uses the Macrovision UPX packer to shrink its ~1.4 MB binary to 275 KB, then writes its own decryptor stub to C:\Windows\FontCacheHost.
    – Attempts memory-only execution via reflective DLL injection to evade EDR hooks for initial 5 minutes before writing to disk.
  • Ransom Note Metadata:
    Note name: _readme.txt placed in every directory.
    Typical ransom demand: $980 (50 % discount = $490) in Bitcoin to wallet 1AZrzinFVYVQ8WvZh6hrbmxiBgPhws7zue.
  • Broader Impact & Notable Victories:
    – Decrypme damaged ~5,000 organizations globally in the first six weeks.
    – High-profile data leaks appeared on cyberpress.one in May 2022 for non-paying victims.
    – Dutch police arrested the principal developer (“Volodymyr O.”) in February 2022, effectively ending new key issuance and spurring the public decryptor.

Stay vigilant: campaigns using renamed extension spoofing (.decrypme. with trailing dot) and bundling with Cobalt Strike beacons have emerged in late 2023. Even with the decryptor, maintain full incident-response playbooks to avoid re-infection.