TECHNICAL BREAKDOWN

File Extension & Renaming Patterns
• Confirmation of File Extension: every encrypted file receives the secondary extension “.eegf” (lower-case).
• Renaming Convention:
– Original: annual_report.xlsx
– After encryption: annual_report.xlsx.eegf
– Some clusters also prepend the victim ID in brackets, e.g. [C3A2F899]annual_report.xlsx.eegf.
– The file’s original name and size are preserved; only content is encrypted.
Detection & Outbreak Timeline
• First submission to public malware repositories: 22-Jan-2024.
• Rapid uptick in telemetry observed throughout February-April 2024; still the most active STOP/Djvu derivative as of May 2024.
Primary Attack Vectors
• Malvertising & “fake-cracked” software (greatest volume):
– Victims search for “Photoshop crack”, “Valorant free coins”, “Windows 11 activator”, etc.
– Google-ads point to torrent/sharehost links that drop a password-protected ZIP; the password bypasses AV heuristics.
• Exploit kits (Fallout EK, Spelevo) redirecting from warez sites.
• Pirated games and key-gens bundled with NSIS installers that quietly run the ransomware.
• No evidence so far of worm-like SMB/RDP propagation—manual post-exploitation may be added by initial-access brokers, but the core .eegf payload is delivered by executable droppers.

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REMEDIATION & RECOVERY STRATEGIES

Prevention
1.1 Remove local-admin rights from daily-use accounts.
1.2 Block executables launched from %Temp%, %LocalAppData%, and C:\Users\\Downloads via Application-Control (Windows Applocker / WDAC).
1.3 Keep the operating system & third-party software fully patched; although .eegf is rarely delivered via exploit, secondary Cobalt-Strike beacons often abuse 1-day bugs.
1.4 Deploy a reputation-based DNS filter that denies newly-registered domains (<30 days old)—most Fallout EK gate domains rotate daily.
1.5 Enforce “Cloud-delivered protection” + “Block at First Sight” in Microsoft Defender (or equivalent). STOP/Djvu’s signing certificates change every few hours; cloud AI blocks far quicker than signature updates.
1.6 Mandatory Office 365 / GSuite attachment sandbox if you allow externally mailed Office docs (prevents follow-up human-operated attacks).
1.7 Air-gapped, password-protected, MULTIPLE backups with 3-2-1 rule. STOP/Djvu will enumerate (and delete) Volume Shadow Copies, so offline destinations are mandatory.
Removal
2.1 Immediately isolate the infected PC from network (unplug Ethernet / disable Wi-Fi).
2.2 Boot into Safe Mode with Networking:
Settings → Update & Security → Recovery → Advanced start-up → Troubleshoot → Startup Settings → 5) Safe Mode with Networking.
2.3 Use a second, clean PC to download and copy on USB:
– Malwarebytes 4.x (free)
– ESET Online Scanner
– Trend Micro Ransomware File Decryptor (even if decryption fails, the tool will kill known STOP mutexes)
2.4 Run full scans in the order above; allow reboots; let each product quarantine findings.
2.5 Manually inspect Scheduled Tasks & Registry Run keys:
– HKCU\Software\Microsoft\Windows\CurrentVersion\Run\*
– C:\Windows\System32\Tasks\*
Delete any entry pointing to a random-name executable in %LocalAppData% (typically 5–8 random characters, e.g. “t8sja.exe”).
2.6 Reboot normally and verify that no new .eegf files appear when you create a test document.
2.7 BEFORE connecting back to the LAN, patch everything, change domain credentials, and force password resets company-wide—attackers frequently drop credential stealers before the ransomware stage.
File Decryption & Recovery
STOP/Djvu variants released after August 2019 use OFFLINE keys + ONLINE keys.
• OFFLINE key: the ransomware encrypts with a hard-coded public key when its C2 is unreachable → decryptable once the corresponding private key is donated to the community.
• ONLINE key: unique per victim → decryption impossible without the criminal’s RSA-2048 private key.
3.1 Determine which scenario applies:
– Download Emsisoft’s “STOP Djvu Decryptor” (current version 1.0.0.7).
– Run it on a PAIR of files: one encrypted .eegf and the original unencrypted copy (exact same file size).
– If the tool reports “No key for New Variant online ID”, your files used an online key → pay-or-recover-via-backup.
– If it says “OFFLINE-ID” followed by a 12-digit victim ID ending in “t1”, check the Emsisoft site later—community volunteers may release that key.
3.2 Cloud-storage rollback:
– OneDrive, Google Drive, Dropbox keep 30-day file versions. Restore BEFORE you run a sync client on the cleaned machine.
3.3 Volume Shadow Copy is deleted in >95 % of cases (vssadmin delete shadows /all) but some external USB drives keep snapshots—worth verifying.
3.4 No free brute-force tools succeed; RSA-2048 is cryptographically unbreakable within a practical timeframe.

Essential Tools/Patches
• Windows 10/11 cumulative updates (no specific CVE for STOP, but removes secondary exploits dropped post-infection).
• Emsisoft STOP Djvu Decryptor: https://www.emsisoft.com/decrypter/stop-djvu
• Malwarebytes AdwCleaner + AV engine (free).
• Microsoft Safety Scanner (expires every 10 days, good for one-off confirmation).
• Personal backup utilities that default to immutable storage: Macrium Reflect 8 (password-protected image), Veeam Agent (with rotated offline drives).

Other Critical Information
• Distinguishing behaviour:
– Drops a text file “_readme.txt” in every folder (identical ransom note across all STOP variants).
– Sets the desktop wallpaper to !RECOVER-FILES!.txt via registry.
– Contacts a sequence of 30+ hard-coded C2s (many with .top / .cyou TLD) before deciding offline vs online key.
– Bundles the AZORult info-stealer, which exfiltrates browser passwords, cookies, and crypto wallets → victims MUST assume credentials are compromised and reset EVERYTHING post-cleanup.
• Broader impact:
– STOP/Djvu is the #1 consumer-level ransomware family since 2020; .eegf is simply the 2024 extension branding.
– Corporate networks usually become collateral damage when employees bring in warez, so the same “consumer” malware can encrypt mapped drives, SharePoint sync folders, and SaaS backups if they are mounted as a drive letter.
– Because private keys for online encryption are never released, payout demands are low ($490 → $980) but volume is high; the ecosystem funds the operators’ continual evolution into new extensions (.eegf today, tomorrow something else).

Stay patched, stay backed-up, and never run “key-gens” on production machines—prevention is the only guaranteed decryption for .eegf.