Akira: Forensic Reverse-Engineering & Architectural Dossier

Akira is a multi-threaded ransomware strain developed in native C++ with static runtime linkage. The platform targets both Windows and Linux/VMware ESXi architectures. Akira implements ChaCha20 stream encryption with RSA-4096 key encapsulation, utilizing the Windows ThreadPool API for high-performance concurrent processing. Large files are processed using intermittent block encryption controlled via the -n command-line argument.

{
  "-p": "Specifies target filesystem path or network mount point for encryption.",
  "-s": "Confines execution to a single designated volume or file path.",
  "-n": "Sets the block encryption stride percentage (e.g., -n 20 encrypts 20% of data across large files).",
  "-k": "Test decryption session key injection parameter.",
  "-l": "Directs console execution traces to a designated local log file.",
  "-v": "Process fork multiplier for parallel directory subtree crawling.",
  "-path": "Target datastore path specifier for Linux / VMware ESXi binary builds.",
  "-encryption_type": "Selects encryption depth (full or partial) on VMware ESXi builds."
}

{
  "description": "Hardcoded configuration structures located in .rdata section with XOR-encoded string arrays",
  "fields": [
    "0x00: RSA-4096 public key modulus (512 bytes) and public exponent",
    "0x204: XOR-encoded ransom note filename: akira_readme.txt",
    "0x218: XOR-encoded appended file extension: .akira (or .powerranges)",
    "0x228: Array of blacklisted directory paths: Windows, ProgramData, Boot, System Volume Information",
    "0x260: Array of excluded file extensions: .exe, .dll, .sys, .akira, .lnk",
    "0x290: Base64-encoded ransom note text incorporating victim negotiation Tor URL",
    "0x400: Magic EOF identifier marker: 4-byte constant 0x22 0x05 0x19 0x93"
  ]
}

{
  "initialization": "Parses command-line arguments (-p, -n, -l). Decodes internal XOR string tables in memory. Initializes Windows ThreadPool environment.",
  "shadowCopyPurge": "Executes PowerShell WMI command: powershell.exe -Command \"Get-WmiObject Win32_ShadowCopy | ForEach-Object { $_.Delete(); }\". Disables recovery: bcdedit.exe /set {default} recoveryenabled no.",
  "processTermination": "Enumerates running processes via CreateToolhelp32Snapshot. Identifies database and backup processes (sqlservr.exe, VeeamDeploymentService.exe) and calls TerminateProcess.",
  "directoryTraversal": "Performs recursive directory search using FindFirstFileW and FindNextFileW. Filters paths against the exclusion blacklist.",
  "cryptographicProcessing": "Submits work items to Windows ThreadPool. Evaluates file size: files under 2 MB are encrypted entirely; files over 2 MB are encrypted in alternating 256 KB blocks according to the -n percentage switch. Encrypts using ChaCha20; wraps key using RSA-4096.",
  "footerAppending": "Appends binary metadata structure at EOF: 12-byte ChaCha20 IV + 512-byte RSA-encrypted key + 4-byte magic marker (0x22051993) + 4-byte percentage indicator. Renames file to .akira.",
  "notePlacement": "Writes akira_readme.txt into every traversed directory."
}

Concrete technical breakdown of functional modules implemented in the Akira binary:

Negotiation and extortion proceed through private Tor V3 Onion services. The dropped ransom note provides an onion address and an affiliate-specific access code. Affiliate operators coordinate data exfiltration via HTTPS REST endpoints prior to deployment of the locker binary.

Indicators of compromise and forensic patterns recorded across laboratory triage: