Ymir ransomware virus – removal and decryption options

Ransomware

Also Known As: Ymir virus

(updated)

Damage level:

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What kind of malware is Ymir?

Ymir is a ransomware-type program. It operates by encrypting files (using ChaCha20 cryptographic algorithm) and demanding ransoms for the decryption.

The filenames of files locked by Ymir are altered by being appended with an extension comprising a random character string. For example, a file initially titled "1.jpg" has appeared as "1.jpg.6C5oy2dVr6".

After the encryption is concluded, Ymir drops ransom notes – "INCIDENT_REPORT.pdf" – into each affected folder. This ransomware also displays another message in a full-screen that precedes the log-in screen.

Screenshot of files encrypted by Ymir ransomware:

Files encrypted by Ymir ransomware (extension comprising a random character string)

Ransom note overview

Ymir's pre log-in screen message states that the victim's network has been compromised. During the attack, files were encrypted, and sensitive data was stolen. Recovery will require payment, and attempts at decryption with third-party tools can damage the files beyond repair. The victim is instructed to inform their superiors of the ransomware infection.

The PDF document created by Ymir provides more information about the attack. It reiterates the key points made in the full-screen displayed before the log-in screen.

Some important information from this note includes the claim that by meeting the ransom demands, the victim will receive the decryption tools, and the stolen data will be deleted from the attackers' services. If they refuse to pay, the exfiltrated content will be made public – such as by being leaked online, sold on darknet forums, or handed over to the media or the victim's competitors. The message details the potential ramifications of a data leak, including the likely significant financial loss.

Before paying, the victim can test decryption by sending the cyber criminals up to three encrypted files, which will be sent back decrypted, alongside proof of the data theft.

Ymir ransomware overview

In known Ymir attacks, the data theft was carried out using RustyStealer, and it preceded the ransomware deployment by two days. Ymir infiltrated systems via PowerShell remote control commands. Multiple tools were used to facilitate the attack and perform malicious actions.

In addition to RustyStealer, these infections involved Process Hacker and Advanced IP Scanner. An elaborate component of said attacks is the manner of their detection evasion, which entails many operations being performed in memory through specific function calls. It was observed that hundreds of calls were made to one of the functions. The purpose was to introduce instructions in small pieces into memory to carry out malicious actions.

The infection's capability to self-spread through local networks was facilitated through the use of WinRM (Windows Remote Management), PowerShell remote control abilities, and the SystemBC malware.

Based on our extensive experience researching ransomware infections, we can infer that decryption is usually impossible without the attackers' interference. The rare exceptions are cases involving deeply flawed ransomware.

Furthermore, victims often do not receive the promised decryption keys/software despite meeting the ransom demands. Therefore, we strongly advise against complying with them. Remember that sending money to criminals supports their illegal activities.

To prevent Ymir ransomware from further encryptions – it must be eliminated from the operating system. However, removal will not restore already compromised files. The only solution is to recover them from a backup (if one was created prior and is stored elsewhere).

Keep in mind that it is best practice to store backups in multiple separate locations, such as remote servers, unplugged storage devices, and others.

Ransomware examples

We have written about numerous ransomware-type programs; Frag, ScpInterlock, and Kasper are merely a few of our newest articles. This malicious software encrypts data and demands payment for the decryption.

However, programs within this classification have two significant differences. Ransomware can use different cryptographic algorithms (symmetric or asymmetric) to encrypt files. Additionally, ransoms can differ greatly (from three to eight digits in USD) depending on the intended victims – i.e., home users vs. large entities (corporations, companies, organizations, etc.).

How did ransomware infect my computer?

Generally, ransomware and other malware are proliferated using phishing and social engineering tactics. Malicious programs are usually disguised as or bundled with ordinary software/media.

Virulent files can be archives (ZIP, RAR, etc.), executables (.exe, .run, etc.), documents (Microsoft Office, Microsoft OneNote, PDF, etc.), JavaScript, and so forth.

Malware (ransomware included) is primarily spread via backdoor/loader-type trojans, drive-by (stealthy/deceptive) downloads, malicious attachments or links in spam emails/messages, online scams, malvertising, dubious download channels (e.g., freeware and third-party websites, P2P sharing networks, etc.), illegal software activation tools ("cracks"), and fake updates.

Some malicious programs can even self-proliferate through local networks and removable storage devices (e.g., external hard drives, USB flash drives, etc.).

Threat Summary:
Name Ymir virus
Threat Type Ransomware, Crypto Virus, Files locker
Encrypted Files Extension Files are appended with an extension composed of a random character string
Detection Names Avast (PDF:MalwareX-gen [Misc]), Combo Cleaner (Gen:Variant.Tedy.726352), ESET-NOD32 (A Variant Of Win64/Filecoder.Ymir.B.gen), Kaspersky (Trojan-Ransom.Win32.Encoder.zmh), Microsoft (Trojan:Win32/Casdet!rfn), Full List Of Detections (VirusTotal)
Ransom Demanding Message INCIDENT_REPORT.pdf
Free Decryptor Available? No
Cyber Criminal Contact qTOX messenger, RecoverySupport@onionmail.org
Symptoms Cannot open files stored on your computer, previously functional files now have a different extension (for example, my.docx.locked). A ransom demand message is displayed on your desktop. Cyber criminals demand payment of a ransom (usually in bitcoins) to unlock your files.
Distribution methods Infected email attachments (macros), torrent websites, malicious ads.
Damage All files are encrypted and cannot be opened without paying a ransom. Additional password-stealing trojans and malware infections can be installed together with a ransomware infection.
Malware Removal (Windows)

To eliminate possible malware infections, scan your computer with legitimate antivirus software. Our security researchers recommend using Combo Cleaner.

Download Combo Cleaner

To use full-featured product, you have to purchase a license for Combo Cleaner. 7 days free trial available. Combo Cleaner is owned and operated by RCS LT, the parent company of PCRisk.com.

How to protect yourself from ransomware infections?

We recommend vigilance when browsing since the Web is full of well-disguised fraudulent and malicious content. Incoming emails, PMs/DMs, SMSes, and other messages must be approached with care. Attachments or links present in suspicious mail must not be opened, as they can be virulent.

Another recommendation is to download only from official and verified sources. Additionally, all programs must be activated and updated using legitimate functions/tools, as those acquired from third-parties can contain malware.

We must stress the importance of having a reputable anti-virus installed and kept updated. Security software must be used to run regular system scans and to remove threats and issues. If your computer is already infected with Ymir, we recommend running a scan with Combo Cleaner Antivirus for Windows to automatically eliminate this ransomware.

Appearance of Ymir ransomware's ransom note "INCIDENT_REPORT.pdf" (GIF):

Ymir ransomware ransom note (INCIDENT_REPORT.pdf) GIF

Text presented in this message:

#? What happened?
Your network has been compromised and attacked by hackers.
All files have been modified.
Sensitive information has been stolen and handed over to our
experts for analysis.


#? Why did this happen?
Your security system was weak, it allowed your company to be
hacked.


#? What are the possible consequences?
You won't be able to use your data, so the company is frozen. You
will lose money every day.
If you refuse to make a deal, your data will be published on the
internet, sold on darknet forums, shared with journalists and your
competitors.
You will suffer reputational damage, your stock will drop in value,
clients and sponsors will lose trust in you.
Also, if the incident becomes public, you will be noticed by law
enforcement agencies and then a long investigation with freezing
of your company will begin.
You'll get multiple fines in excess of the deal.

 

#? What do I get if I make a deal?
You get file recovery software. We'll remove the stolen data from our servers and provide proof.
You'll get an incident report and recommendations for protection.
You'll get a guarantee that our team will add you to our whitelist of
untouchable companies and we'll never come back to you again. We will not report the incident to anyone.


#? # Why are you doing this?
We're only interested in the money. We don't care about the rest. We also take pleasure in what we do.


#? How can I trust you?
You have no choice, either you lose everything or you trust us. We don't plan to deceive you. We operate in a public space, every
action we take is discussed.
If we defraud even 1 company, we will never be able to make a
good deal. We will definitely recover your files and we will definitely keep
everything confidential.
We are specialists with years of experience and we respect
ourselves and our reputation.
You'll see that we're a bargain when you contact us.


#? How do I proceed if I don't believe a word you say?
You can go to the recovery or the enforcers, but it will definitely
cost you more than dealing with us.
Recovery will buy our software with your token and sell it to you at
a 300% markup.
The enforcers will trample your company, talk to the lawyers, they
will tell you the consequences.

 

#? I'm the administrator of this network, what do I do?
Don't try to make a deal on your own, you won't have enough
salary for a few years.
Report the incident to your bosses. They'll find out anyway. We
have their contacts and we'll let them know in three days if no one
contacts us.
If you try to rebuild the network alone and hide the incident from
your bosses, you'll delay the inevitable. At some point, they'll hear
about it on the news and be furious that you denied them the
opportunity to save their company.


#? What do I do?
The first thing you should do is inform your bosses about the
incident.
You'll have to pay us to recover your files. Only we have the unique
token.
Don't try to use any third-party applications to recover your files,
they may be damaged irretrievably.
You need to contact us
You can send us 1-3 modified files and we will prove that we can
recover them. We will provide proof of the stolen data.

 

RecoverySupport@onionmail.org
To contact us, install qTOX messenger.
hxxps://github.com/qTox/qTox/releases/download/v1.17.6/setupqtox-x86_64-release.exe
Add our contact and we can make a deal.


Tox ID:
CF9AE1B27EAA4BF8C223735BEA15AAE23D5BA312B9D9061C805ABD99C373530DBDCC18B7C3BF

Screenshot of the full-screen message displayed by Ymir before the log-in screen:

Ymir ransomware pre log-in screen message

Text presented in this file:

IMPORTANT
What happened? Your network has been compromised and attacked by hackers. All files have been modified. Sensitive information has been stolen and handed over to our experts for analysis. What do I do? The first thing you should do is inform your bosses about the incident. You'll have to pay us to recover your files. Only we have the unique token. Don't try to use any third-party applications to recover your files they may be damaged irretrievably. To contact us read the INCIDENT REPORT file carefully

Ymir ransomware removal:

Instant automatic malware removal:

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Removal and file recovery procedure

If your files are encrypted with a new extension and a ransom note has appeared, you've been hit by ransomware. Don't pay. The procedure below works in order: contain the infection, identify the variant, remove the ransomware itself (so anything you restore doesn't get re-encrypted), and try to recover files using free decryption tools, Windows Volume Shadow Copies, or backups. Run a full system scan with Combo Cleaner to remove the infection - then move on to file recovery.

Common ransomware behaviors

VisibleEncrypts your files and renames them

The ransomware reads each file, encrypts the contents with the attacker's public key, and writes the encrypted bytes back to disk. Most variants also rename the file by appending a new extension - .net, .locked, .crypt, .lockbit, .djvu, etc. Without the matching private key, the encrypted files cannot be opened normally. Recovery depends on a free decryption tool, a recoverable Volume Shadow Copy, or a clean backup.

File Explorer showing files with ransomware-encrypted extension
VisibleDrops a ransom note in every encrypted folder

A text or HTML file (usually named HOW_TO_DECRYPT.txt, README.txt, _readme.txt, or similar) is placed in every folder that contains encrypted files. The note explains the situation, lists a payment amount in cryptocurrency, gives a deadline, and provides a contact email or .onion site. Save the note - don't delete it. Its exact wording, the email address, and the bitcoin wallet are how you identify the variant in the next phase.

Example ransom note text file with redacted contact information
VisibleReplaces the desktop wallpaper

Many ransomware variants change the Windows wallpaper to a black or red image with the ransom message and instructions. The wallpaper is just a visual scare tactic - it doesn't add any actual capability and reverts to normal once the ransomware is removed. Photograph it before removal in case the contact details are useful for variant identification or for reporting to authorities.

Example ransomware desktop wallpaper takeover
HiddenDeletes Volume Shadow Copies

One of the first things modern ransomware does after launching is run vssadmin delete shadows /all /quiet to wipe Windows' built-in Volume Shadow Copies - the snapshots that Previous Versions and System Restore rely on. Some ransomware doesn't fully succeed (especially on systems where the user lacks full admin rights), leaving partial shadow copies recoverable. Phase 4 step 11 covers how to check what survived.

Command prompt vssadmin list shadows output
HiddenDisables Windows Defender and other security tools

Before encrypting, the ransomware tries to silence anything that could alert you or block it - Windows Defender real-time protection, third-party antivirus services, backup agents (Veeam, Acronis), and sometimes the Windows Event Log service. It often modifies Group Policy or registry keys to keep these off after reboot. Phase 3 step 9 explicitly turns Tamper Protection back on so the next ransomware attempt can't repeat the trick.

Windows Security with Defender disabled by malware
HiddenSpreads laterally to other PCs on the network

Network-aware ransomware (LockBit, Conti, BlackCat, Akira families) doesn't stop at the first machine. It scans for SMB shares, mapped drives, and other PCs on the same network, then encrypts whatever it can reach. On Windows domains, a single compromised user with admin rights can lead to all-domain encryption. This is why Phase 1 step 2 disconnects the network as the very first action - it stops the spread immediately.

HiddenSteals data before encrypting (double extortion)

Modern ransomware (LockBit, BlackCat / ALPHV, Akira, Cl0p, Royal) almost always exfiltrates data before encrypting. The attacker then runs a "double extortion" play: pay the ransom for decryption, plus pay again to prevent the stolen data from being leaked on the group's leak site. Paying the first ransom does not get the leaked data back - assume that anything the ransomware could read was uploaded. This is one more reason not to pay: the data is already out.

Tools you'll need
Combo Cleaner Antivirus 7-days free trial
Recommended primary scanner. VB100 certified. Removes the ransomware infection so file recovery doesn't get re-encrypted.
Built into Windows. Scans before Windows fully loads to catch persistence the running scanners miss.
Microsoft's free on-demand scanner. Always-current signatures - the binary expires every 10 days.
ID Ransomware Free · web
Upload a ransom note and a sample encrypted file - identifies the variant family and tells you whether a free decryptor exists.
Joint project of Europol, Dutch Police, and security vendors. Free decryption tools indexed by ransomware family.
Browse Windows Volume Shadow Copies as a normal file tree - useful when ransomware partially failed to delete them.
Recuva Free
Deleted-file recovery. Long-shot for ransomware - only helps if the variant deleted unencrypted originals before encrypting copies.
Phase 1~ 5 min
Don't pay & contain

1

Don't pay the ransom

1 min · read⚠ Do not skip

Paying the ransom does not guarantee you'll get your files back. Major ransomware response studies consistently show that a meaningful percentage of paying victims either receive a non-working decryptor, only partial decryption, or no decryptor at all. Beyond that:

  • Paying confirms you as a willing target - re-attack rates within 12 months are high
  • Several ransomware groups have been sanctioned (US OFAC, UK OFSI). Paying these groups may be illegal under sanctions law in your country
  • The ransom funds the next attack - on you or someone else
  • Modern ransomware almost always exfiltrates data first, so paying doesn't get the leaked data back. Assume anything the malware could read was uploaded
  • Decryptors, even when they work, often leave files corrupted because the encryption itself was buggy or rushed

The path below tries every legal, free recovery option first. Pay only as an absolute last resort, after consulting a lawyer and your country's cyber crime authority.

2

Disconnect from the network and log out of cloud storage

2 minNo tool needed

Pull the Ethernet cable and turn off Wi-Fi on the affected PC. If multiple computers share the network, do the same on every machine you suspect could be affected, including any servers and NAS units.

Then sign out of cloud storage clients (OneDrive, Dropbox, Google Drive, iCloud) from their app settings. If you can, pause the sync. Some ransomware uses the running sync client to push encrypted versions over your clean cloud copies.

Why this matters

Modern ransomware spreads laterally across SMB shares, mapped drives, RDP, and reachable network neighbors. Disconnecting stops the spread the moment you do it. Logging out of cloud sync clients prevents the ransomware from encrypting the cloud copies of your files via the sync API.

3

Unplug external drives and USB storage

1 minNo tool needed

Safely eject any external drives, USB sticks, SD cards, and network-attached storage shares - then unplug them. If a drive was connected when the ransomware ran, the files on it may already be encrypted, but unplugging stops further damage.

Critically: don't reconnect any drive (including your most recent backup) to this PC until the ransomware is removed in Phase 3. Reconnecting an external backup to an actively-infected PC is the most common way that backup gets encrypted too.

Phase 2~ 5 min
Identify the variant

4

Save the ransom note and a sample encrypted file

2 min

Copy the ransom note and one small encrypted file (under 1 MB) to a USB stick, or photograph the note with your phone. You'll need both for the variant identification step.

The ransom note is usually one of:

  • A .txt file in every encrypted folder (typically HOW_TO_DECRYPT.txt, README.txt, or _readme.txt)
  • An .html file with the same purpose
  • A changed desktop wallpaper - photograph it
  • A lock-screen interrupt that runs at startup - rarer
Important

Don't delete the note. Variant identification depends on its exact wording, the contact email, and the bitcoin wallet address. The note is also evidence if you report to authorities.

5

Identify the variant with ID Ransomware

Tool: ID Ransomware3 min

From a clean device (your phone is fine, or another PC that wasn't on the affected network), visit id-ransomware.malwarehunterteam.com. Upload the ransom note and the sample encrypted file. The site identifies the variant family and tells you whether a free decryptor exists.

Pro tip

ID Ransomware is run by the Malware Hunter Team. Files you upload are kept private - they're used for analysis, not published. If you're concerned about uploading data anyway, you can paste the contact email and bitcoin wallet from the note - those are often enough for identification.

ID Ransomware identification result for a sample variant
Phase 3~ 30-45 min
Remove the ransomware

The ransomware itself must be removed before any file recovery. If it's still active, anything you restore in Phase 4 gets re-encrypted within minutes.

6

Boot to Safe Mode with Networking and download the scanners

5 min

Safe Mode loads only the minimal Windows drivers, which prevents most ransomware from auto-running while you set up the scanners.

Windows 11: open Settings → System → Recovery, click Restart now next to Advanced startup. After the restart, click Troubleshoot → Advanced options → Startup Settings → Restart, then press 5 or F5.

Windows 10: click the Windows logo, hold Shift, click the Power icon and choose Restart. From the Choose-an-option screen, click Troubleshoot → Advanced options → Startup Settings → Restart, then press F5.

Once Safe Mode has loaded, turn Wi-Fi back on and download Combo Cleaner (used in step 8) and Microsoft Safety Scanner (used in step 9). Save both installers to your Desktop, then disconnect Wi-Fi again before scanning.

7

Run Microsoft Defender Offline

Tool: Built into Windows15 min

Reboot to normal Windows. Open Windows Security → Virus & threat protection → Scan options. Select Microsoft Defender Antivirus (offline scan) and click Scan now. The PC restarts into a stripped-down environment and scans the disk before Windows fully loads.

Why this comes first

Some ransomware variants drop bootkit components or kernel hooks that hide from any scanner running on the same Windows session that's already infected. A pre-boot offline scan sees the disk before the malware can load itself.

Recommended antivirus
Combo Cleaner

VB100 certified. Includes anti-trojan, registry/persistence scanning, and anti-spyware in one pass. The 7-day free trial is available.

Download Combo Cleaner
8

Run a full Combo Cleaner scan

Tool: Combo Cleaner20-40 min

Run the installer you downloaded in step 6 and start a full system scan (not the quick scan). Let it complete, review what it detected, and apply the recommended actions. Combo Cleaner quarantines the ransomware executable and the registry / scheduled-task entries that re-launch it on reboot.

Combo Cleaner full system scan results showing the detected ransomware family
9

Run Microsoft Safety Scanner and re-enable Defender

Tool: MSERT15 min

Run Microsoft Safety Scanner (MSERT.exe) as a second-opinion full scan. The binary expires every 10 days so the copy you downloaded has the latest signatures.

Once it finishes, open Windows Security → Virus & threat protection → Manage settings and confirm Real-time protection, Cloud-delivered protection, and Tamper Protection are all on. Many ransomware variants disable Defender during the attack - this is where you switch it back on so the next attempt can't repeat the trick.

Why a second scan

Different scanning engines catch different threats. Running an additional Microsoft scan after Combo Cleaner is the most underused verification step in malware removal - and free.

Phase 4~ 30-60 min · results vary
Try to recover files

Try the steps in order. The first decryptor that works ends the recovery process - no need to do all four.

10

Check the No More Ransom Project for a free decryptor

Tool: nomoreransom.org★ Cleanest path if listed5 min

Visit nomoreransom.org and search the Decryption Tools list for the variant name returned by ID Ransomware. The project is run by Europol, the Dutch Police, and security vendors - everything listed is legitimate and free.

If a decryptor exists, download it onto a clean PC, copy it across, and follow its instructions exactly. Decryptors usually want you to point them at a sample encrypted file plus its known unencrypted version (sometimes any image you previously had a backup of works).

Free decryptors exist for parts of the STOP/Djvu, GandCrab, REvil, Avaddon, Conti and Hive families, among others. Most modern variants don't have public decryptors - if yours isn't listed, that's expected; move to the next step.

No More Ransom Project decryption tools list
11

Try Windows Volume Shadow Copies

Tool: Shadow Explorer / vssadmin15 min

Windows automatically creates Volume Shadow Copies of files when System Restore points are made or scheduled backups run. Most ransomware tries to wipe these (vssadmin delete shadows /all /quiet), but the deletion sometimes fails partially - especially if the running user doesn't have full admin rights. When it does fail, snapshots survive that contain pre-encryption versions of your files.

First, check what's there. Open Command Prompt as Administrator and run:

vssadmin list shadows

If you see entries listed, shadow copies survived. To restore from them:

  • Built-in: right-click any folder → Properties → Previous Versions tab. Pick a snapshot dated before the infection and restore.
  • Better tool for browsing: install Shadow Explorer (free). It shows all snapshots as a normal file tree and lets you copy out only the files you want.
Why check this even when there's a decryptor

Shadow Copies recover the original files exactly, with no risk of decryption errors. If they survived, this is faster and cleaner than running a decryptor on the encrypted set.

Shadow Explorer browsing pre-infection Volume Shadow Copies
12

Restore from cloud or external backup

Tool: your backup software30 min

If you have a backup that pre-dates the infection, this is the cleanest recovery available. Important precautions:

  • Don't reconnect a backup drive until Phase 3 is complete. If the ransomware is still active, plugging in the backup encrypts it too.
  • For cloud backups (OneDrive, Dropbox, Google Drive, iCloud), use the Version History feature to roll individual files back to pre-encryption versions.
  • OneDrive specifically has a "Restore your OneDrive" feature: if it detected mass file changes, you can roll back the entire account up to 30 days. Sign in at OneDrive on the web, click the Settings gear, and choose Restore your OneDrive. Microsoft 365 subscribers also get ransomware detection alerts; non-subscribers get one free recovery.
  • Verify the restored files open correctly before you delete the encrypted set. Test a few documents, photos, and any database / project files.
13

Try Recuva as a last-resort recovery

Tool: Recuva30 min

Recuva is a long shot, not a primary recovery tool. Most modern ransomware encrypts files in place - it reads the original, encrypts the data, and writes the encrypted bytes back to the same disk location. In that case, the original isn't deleted, just rewritten - and Recuva has nothing to find.

But for older or simpler variants that deleted originals before creating encrypted copies (rather than encrypting in place), Recuva can sometimes pull the originals from unallocated disk space. Worth trying as a last resort, especially before you use the disk much further.

If you try it:

  • Stop using the disk as much as possible - every disk write reduces recovery odds
  • Run Recuva from a USB stick, not from the affected disk
  • Use Deep Scan mode (slower but the only mode worth running for this scenario)

Don't skip the steps above expecting Recuva to bail you out. It works in maybe 5-20% of cases, depending on the variant and how soon you try.

Phase 5~ 20 min + ongoing
Report & prevent re-infection

14

Report the attack to authorities

10-20 min

Even if your files aren't recovered, your report helps authorities track variants, attribute groups, and warn future victims. In some jurisdictions (especially the US and UK) early reporting can sometimes help recall a wired ransom payment via banking partners.

United States: ic3.gov (FBI) + stopransomware.gov (CISA)
United Kingdom: reportfraud.police.uk (Report Fraud, the successor to Action Fraud) + NCSC
Australia: ReportCyber
Germany: BKA
Netherlands: Politie
Poland: CERT Polska
Portugal: CNCS
EU (other): your national CERT

Save the report number - banks, insurers, and credit bureaus will ask for it. If you operate a business, you may also have legal disclosure obligations (GDPR in the EU, state breach laws in the US) that run on a 72-hour clock.

15

Plan 3-2-1 backups going forward

30 min initial

The single best defense against ransomware is a tested backup. Use the 3-2-1 rule:

  • 3 copies of your data
  • 2 different storage media (e.g., internal drive + external drive)
  • 1 offline / air-gapped copy (an external drive that isn't always connected)

Recommended cadence:

  • Daily: cloud sync (OneDrive, Dropbox, Google Drive) - convenient, but vulnerable if the ransomware reaches the sync folder. The Version History feature is what saves you
  • Weekly: external drive that you connect briefly, then disconnect - the air-gap is what protects against ransomware
  • Monthly: a second external drive stored off-site (different physical location) - protects against fire, theft, flood
Important

Test the backup at least once. Open a few files from it, check sizes match, restore one to a different folder. An untested backup isn't a backup - it's a hope.

16

Patch the entry point and monitor for 30 days

5 min/day · 30 days

Most reinfections happen via the same vector that worked the first time. Until you've patched the entry point, watch for:

  • Unusual disk activity, unexpected file modifications, or unfamiliar processes in Task Manager
  • Unexpected reboots or new accounts you didn't create
  • Defender or your antivirus turning itself off again

Common entry vectors and what to do about each:

  • Phishing email with a malicious attachment - review email filters and train yourself / staff to recognise the patterns - see pcrisk's Phishing/Scam reference
  • Exposed RDP with weak passwords - disable Remote Desktop from Settings → System → Remote Desktop if you don't need it. If you do, put it behind a VPN and require a long password plus MFA
  • Unpatched VPN appliances or public-facing apps - check the vendor's advisories page and apply the latest firmware
  • Cracked / pirated software - was the most common vector for STOP/Djvu in particular. Don't run software from torrent sites

Run a Combo Cleaner scan weekly for the first month. Update Windows, browsers, and applications aggressively.

Important: Removing a ransomware infection requires a full system scan, not a manual file delete. If you're not confident with the manual procedure, run an automated scan with Combo Cleaner and Windows Defender and stop there - that combination removes the vast majority of consumer ransomware variants. Then move to Phase 4 for file recovery, or to Phase 5 if your files are unrecoverable and you need to start fresh from a clean Windows install.

Frequently Asked Questions (FAQ)

How was my computer hacked and how did hackers encrypt my files?

Victims themselves often open ransomware executables, as they are typically presented as regular files. This malware is mainly distributed via drive-by downloads, trojans, untrustworthy download sources (e.g., freeware and free file-hosting websites, P2P sharing networks, etc.), online scams, spam mail, malvertising, illegal program activation ("cracking") tools, and fake updates.

How to open files encrypted by Ymir ransomware?

Continued file usage necessitates decryption. In other words, encrypted files cannot be accessed unless they are decrypted.

Where should I look for free decryption tools for Ymir ransomware?

If you have experienced a ransomware infection, we recommend looking up the No More Ransom project website (more information above).

I can pay you a lot of money, can you decrypt files for me?

We do not offer decryption services. It must be mentioned that restoring encrypted files is usually impossible except for cases involving seriously flawed ransomware. Therefore, third-parties offering paid decryption are often scams or middleman services between victims and criminals.

Will Combo Cleaner help me remove Ymir ransomware?

Combo Cleaner will scan your device and remove active ransomware infections. It is noteworthy that while using an anti-virus is the first step in ransomware recovery – security software cannot decrypt data.

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Tomas Meskauskas

Tomas Meskauskas

Expert security researcher, professional malware analyst

I am passionate about computer security and technology. I have an experience of over 10 years working in various companies related to computer technical issue solving and Internet security. I have been working as an author and editor for pcrisk.com since 2010. Follow me on Twitter and LinkedIn to stay informed about the latest online security threats.

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