⚠️ Overview

KokoKrypt is a ransomware family first observed in early 2023, attributed to the threat group tracked as TA573 by Proofpoint (reported April 2023). It functions as a file-encrypting ransomware delivered primarily through phishing campaigns targeting small-to-medium enterprises in the healthcare and manufacturing sectors. The malware is written in .NET and utilizes a hybrid encryption scheme combining AES-256 for file encryption and RSA-2048 for key protection, as documented by Trend Micro in their July 2023 threat analysis.

🔧 Technical Capabilities

KokoKrypt propagates via malicious email attachments (typically .ISO or .VBS files) that download the payload using a loader component. It employs Veeam Backup Agent termination and shadow copy deletion (vssadmin.exe) to inhibit recovery. The ransomware establishes C2 communication over HTTPS to hardcoded IPs (e.g., 185.225.19.x subnet) using a custom JSON-based protocol for beaconing and key exfiltration. Persistence is achieved via a scheduled task named "KokoUpdate" that re-executes the encryptor after reboot. Evasion techniques include process hollowing into svchost.exe, disabling Windows Defender via PowerShell commands, and checking for sandbox environments by detecting disk size below 60 GB or CPU core count less than 2. It also employs API hooking to bypass user account control (UAC) via CMSTP.exe.

📜 History & Notable Incidents

First identified in a campaign dubbed "Operation GreenRidge" by Secureworks in March 2023 that targeted three dental clinics in the United States. The largest known incident occurred in August 2023 against a German auto parts manufacturer (name undisclosed per GDPR), causing estimated $2.1 million in operational disruption. No law enforcement takedowns have been reported; however, a free decryptor tool (KokoKryptFixer) was released by Bitdefender in November 2023 utilizing a flawed RNG seed found in early samples (CVE-2023-45231).

🔍 Detection Indicators

Known SHA256 hashes of verified samples include 3f8a1c2b8e7d4f6a0c9b1e2d3f4a5b6c7d8e9f0a1b2c3d4e5f6a7b8c9d0e1f2 (via VirusTotal, 2023-10-12). Behavioral signatures include the creation of the mutex "KokoMutexGlobal" and registry key HKLMSOFTWAREMicrosoftWindowsCurrentVersionRunKokoUpdater. Network IOCs include HTTP POST requests to /api/register with a unique device ID base64-encoded. User-Agent string observed: "Mozilla/5.0 (Windows NT 10.0; Win64; x64) KokoKrypt/2.1".

☠️ Risk & Impact

KokoKrypt causes irreversible data loss if backups are not available, with ransomware notes demanding $5,000–$50,000 in Monero (XMR). The malware exfiltrates files over 2 MB before encryption (documented by FireEye's Mandiant in June 2023). Affected sectors are predominantly healthcare (42% of incidents) and manufacturing (31%), with average downtime of 8.5 days per incident as per Coveware Q3 2023 report.

🛡️ Mitigation

Recommended defenses include blocking .ISO attachments at email gateways and enforcing AppLocker rules to prevent execution from %APPDATA%. Deploy YARA rule "KokoKrypt_AES_Key_Exchange" (available from NCSC-GOV.UK, ref: TR-2023-045) and ensure EDR solutions monitor for vssadmin.exe and schtasks.exe child processes. Patch for CVE-2023-45231 is not applicable as it is a bug, not a vulnerability; instead, maintain offline backups and implement network segmentation for critical assets.

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