What is the EIUR file format?
A .eiur file is an ordinary file that has been encrypted by EIUR ransomware, a variant of the widespread STOP/Djvu family. This strain appeared around mid-2022 and behaves like its many siblings, differing mainly in the four-letter extension it appends. When EIUR infects a Windows PC it scrambles documents, photos, databases and videos with the Salsa20 cipher, protects that key with RSA-2048, and renames each file so budget.xlsx becomes budget.xlsx.eiur. It then drops a ransom note called _readme.txt in every affected folder, demanding $980 in Bitcoin (or $490 within 72 hours) and listing the contact addresses [email protected] and [email protected].
To work quickly the malware encrypts only the first 150 KB of each file, which is why large files are sometimes partly intact. Seeing .eiur files means the ransomware executed on your machine, and it may have installed a password-stealing trojan alongside the encryptor.
Security & safety
RISK: HIGHA .eiur file is itself inert ciphertext, but its presence means active ransomware ran on the machine and may still be resident along with a bundled information-stealer such as RedLine or Vidar. Do not pay the ransom; there is no guarantee of a key and payment funds further attacks. Isolate the device, run a reputable anti-malware scan to remove the executable, then attempt recovery only from backups or the Emsisoft decryptor.
Format details
in a nutshellPrograms that open EIUR files
Windows5 apps
Emsisoft Decryptor for STOP Djvu
Free Download and run the decryptor, let it scan your drives, and it will restore files that were encrypted with a known offline key; it reports when an online key was used and files cannot be recovered.
Malwarebytes
Freemium Run a full scan to detect and quarantine the EIUR ransomware executable and any bundled stealer before attempting any file recovery.
Windows System Restore
Built-in Roll the system back to a restore point created before the infection to recover unencrypted copies, if restore points survived the attack.
ShadowExplorer
Free Browse Volume Shadow Copies to pull earlier, unencrypted versions of files, though STOP/Djvu usually deletes shadow copies.
PhotoRec
Open-source Carve deleted original files from the disk after encryption, since STOP/Djvu often encrypts a copy and deletes the source, leaving recoverable remnants. Technical details
deep spec| Encoding | Salsa20 stream cipher applied to file contents |
| Encryption | Salsa20 for data; the Salsa20 key is protected with RSA-2048. Each victim receives either a shared 'offline' key (used when the C2 server is unreachable) or a unique 'online' key fetched from the attacker server. |
| Byte order | N/A (opaque ciphertext) |
| Container | Original file wrapped with encrypted payload plus an appended block containing the encryption marker and victim key/ID data |
| Partial Encryption | Only the first 150 KB of each file is encrypted, which is why large files are sometimes partially recoverable or repairable |
| Typical size | Same as the original file plus a small appended overhead |
| Structure | Original data encrypted in-place at the start of the file, with a trailing signature and embedded key/personal-ID block; the '.eiur' extension is appended to the original filename (for example 'photo.jpg' becomes 'photo.jpg.eiur'). |
| Integrity | None; no integrity field is present |
| Ransom Note | _readme.txt dropped in every folder with encrypted files and on the desktop |
| Ransom Amount | USD 980, reduced to USD 490 if the victim contacts the attackers within 72 hours, payable in Bitcoin |
| Attacker Contacts | [email protected] and [email protected] |
| Malware Family | STOP/Djvu ransomware |
| Platforms | Windows |
| Notes | EIUR spreads through cracked software, key generators, fake installers and malicious downloads, and often bundles a secondary information-stealer (such as RedLine or Vidar). Files encrypted with a known offline key can sometimes be recovered with Emsisoft's free decryptor; files encrypted with a unique online key cannot be decrypted without the attacker's private key. |
| Released | 2022 (STOP/Djvu variant appeared around late June 2022) |
EIUR conversions
Community Q&A
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