UmbreCrypt virus: what it is and how to remove it

You cannot open them by renaming or with another program, because the content of files ending in .dim has been encrypted. The only ways back are a working decryptor for the family, or clean copies from elsewhere:

• OneDrive versions
• File History
• an offline backup drive
• Previous Versions if the ransomware did not delete them

Identify the family first by uploading the ransom note and one encrypted file to ID Ransomware or No More Ransom. Avoid websites and programs that promise to open any encrypted file; they do not work and some are scams.

Nobody can promise a date. When we last checked, on 6 October 2026, no free decryptor is known. Decryptors usually appear after one of three events:

• police seize the attackers' servers and keys
• the authors leak or publish the master keys
• researchers find a mistake in how the ransomware generates keys

Some families got a tool within weeks, others never. Keep the encrypted files and the note on an external drive, check No More Ransom every few months, and follow news about the UmbreCrypt virus family. A decryptor may need an original file, so keep any unencrypted copies too.

Only if a decryptor already exists or the company pays the attackers for you. Some "ransomware recovery" services advertise that they can decrypt families with no known flaw; in practice they negotiate with the attackers and add their own fee. Others use the same free tools listed on No More Ransom.

Before you hire anyone, ask in writing how they will recover the files, whether they will contact the attackers and what happens if they fail. A legitimate service answers clearly. If a free decryptor exists for your family, you can run it yourself.

We advise against it, and so do the FBI, Europol and national cyber agencies. Payment does not guarantee a working tool: some attackers never reply, some tools damage files, and some variants have no decryptor at all. Paying also funds further attacks and can make you a target again.

Before considering payment, try every recovery option in this guide and report the attack. Companies must involve their legal adviser and insurer, because payments to sanctioned groups can be illegal. If files are truly irreplaceable, store the encrypted copies and wait; decryptors sometimes appear later.

The way UmbreCrypt virus spreads has not been documented yet, so look at your own recent activity. On home PCs, ransomware most often comes with cracked programs, game cheats, key generators and fake updates, or with an e-mail attachment that was opened. On business networks, attackers usually log in through Remote Desktop with a stolen or guessed password.

Think back to what was downloaded or installed in the days before files that end in .dim and no longer open, and check the Downloads folder and Installed apps sorted by date. Keep anything suspicious for your report, but do not run it again.

We do not know yet. Nothing published so far shows data theft by UmbreCrypt virus, but the only confirmed sign is files that end in .dim and no longer open, which says nothing about what happened before. Many current ransomware attacks copy files or run a password stealer first, so it is wise to act as if they did.

From a clean device, change the passwords that were saved in the browsers on this PC, starting with e-mail and banking, sign out of all sessions and turn on two-step verification. Watch bank statements and account activity for the next few weeks.

Not necessarily. Ransomware names come from the file extension, the note or a word in the code, so unrelated families often end up with similar names, and one family can appear under several names. The difference matters: a decryptor or advice for one family does not fit another and can damage files.

Compare the ending added to your files and the exact name of the note with the summary table at the top of this guide, then upload the note and one encrypted file to ID Ransomware from a clean device. If the result names another family, follow the guide for that family instead.

It can. Ransomware encrypts every drive and network share it can reach while it runs, so external disks, USB sticks and shared folders connected during the attack may also have files ending in .dim. Disconnect everything now, then check each device from a clean computer.

Do not plug a backup drive into the infected PC until the ransomware has been removed with an offline scan. Cloud folders such as OneDrive sync the encrypted versions, but they keep earlier versions you can usually restore.

Unfortunately not. Deleting the program only ends the attack; every file that already has the .dim ending stays encrypted, because decryption needs a key that only the attackers hold.

That is why this guide separates removal from recovery. First make sure UmbreCrypt virus is gone with an offline scan, then work through the recovery list:

• backups
• OneDrive history
• Previous Versions
• copies on other devices and
• if one exists
• a decryptor

Do not rename or edit the encrypted files in the meantime, and keep them even if nothing works today.

Fortect scans Windows for malware and unwanted programs and repairs the system files and settings they change, and its free scan shows what it finds on your PC before you decide anything.

For UmbreCrypt virus, follow the plan above as well: the browser steps take back permissions and settings that no scanner treats as a threat, and uninstalling the program that brought it removes the source.

Run Microsoft Defender's full scan and, if anything was found, its offline scan as a second opinion. If the symptoms are gone after the plan and both scans are clean, there is nothing more to do.