What is the ODIN file format?
An .odin file is a personal file that has been encrypted by the Locky ransomware. Locky is a Windows malware family that first appeared in early 2016 and locks documents, photos, databases and archives, then demands payment for their return. Around September 2016 the operators switched the extension they appended from .zepto to .odin, naming the variant after the Norse god. Researchers at Fortinet found the .odin code was 98-99% identical to the earlier .zepto build, so it is the same malware wearing a new label.
When Locky runs, it scans for roughly 400 file types, encrypts each one with AES-128, and locks the AES key inside RSA-2048 encryption. It then renames every file to a hexadecimal identifier such as 5FBZ55IG-S575-7GEF-2C7B-5B22862C2225.odin, discarding the original name. It also deletes Windows Shadow Volume Copies and drops ransom notes named _HOWDO_text.html and _HOWDO_text.bmp. Finding .odin files means the computer was infected, not that you own an unusual format.
Security & safety
RISK: HIGHThe presence of .odin files means the computer was hit by active ransomware. The .odin files themselves are inert encrypted data and cannot execute, but they signal that Locky ran on the system, deleted shadow copies and may still be present. Never pay the ransom without expert advice, and treat the machine as compromised until it is fully cleaned and, ideally, wiped and rebuilt from a trusted backup.
Format details
in a nutshell- Samsung Odin firmware package - The Odin flashing tool for Samsung Galaxy devices uses firmware files, but those are typically .tar or .tar.md5 archives rather than a .odin extension. Unrelated to the ransomware.
- ODIN application data - A handful of niche applications have used .odin for internal data or backup files. These are legitimate and unrelated to Locky.
Programs that open ODIN files
Windows4 apps
Malwarebytes
Freemium Run a full scan to detect and remove the Locky infection before attempting any recovery, since the encrypted .odin files themselves cannot be opened.
Emsisoft Anti-Malware
Paid Scan the machine to clean out the ransomware, then check Emsisoft's decryptor catalog to confirm whether any tool covers your variant (none exists for Locky .odin).
Windows File Recovery / Shadow Explorer
Free Browse Volume Shadow Copies to restore earlier unencrypted versions of the files, though Locky usually deletes these.
ID Ransomware
Free Upload a ransom note and an .odin sample to confirm the exact ransomware family and whether any decryption is currently possible. Technical details
deep spec| Encoding | AES-128 (ECB mode) file encryption with the AES key protected by RSA-2048 |
| Byte order | N/A (encrypted ciphertext) |
| Container | None; the original file is overwritten in place as raw ciphertext with a renamed filename |
| Encryption | RSA-2048 + AES-128. The AES session keys are generated server-side by the attacker's command-and-control infrastructure, so the private key needed for decryption never stays on the victim machine. |
| Typical size | Roughly the same size as the original encrypted file |
| Structure | The plaintext of a targeted document, image, database or archive is replaced by AES-128 ciphertext. The file is then renamed to a hexadecimal identifier of the form [8]-[4]-[4]-[4]-[12] followed by the .odin extension (for example 5FBZ55IG-S575-7GEF-2C7B-5B22862C2225.odin). The original name and extension are not preserved on disk. |
| Platforms | Windows |
| Notes | Locky's .odin variant targets roughly 400 to 460 file types across documents, databases, images and archives. It deletes Windows Shadow Volume Copies to block local recovery and drops ransom notes named _HOWDO_text.html, _HOWDO_text.bmp and _[2-digit-number]_HOWDO_text.html. It is delivered by spam email carrying WSF/JS script attachments or macro-laden Office documents that download an encrypted DLL and run it via rundll32.exe. Despite the name, victims are infected by Locky using the .odin extension, not a separate 'Odin' malware family; code comparison shows a 98-99% match with the earlier .zepto variant. |
| Released | September 2016 |
ODIN conversions
Community Q&A
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