AUF Ransomware

What is AUF?

Discovered by Jakub Kroustek, AUF is a ransomware-type program and a new variant of Dharma ransomware. Like most other computer infections of this type, AUF encrypts data and delivers a ransom message. In this case, it generates a "FILES ENCRYPTED.txt" file and opens a ransom demand pop-up window.

It also changes all filename extensions of encrypted files by adding ".AUF" plus a unique victim ID and the ransomware developer's email address. For example, "1.jpg" might become "1.jpg.id-1E857D00.[Decisivekey@tutanota.com].AUF".

The message within the "FILES ENCRYPTED.txt" text file states that AUF ransomware has encrypted (locked) all data. To recover compromised files, victims are required to contact AUF's developers by sending an email to decisivekey@tutanota.com or decisivekey@cock.li.

The pop-up window informs ransomware victims that their computers are infected due to a 'security problem'. The ransom message contains a unique ID for use when contacting cyber criminals via one of the emails. When contacted, they will state the cost of the decryption tool, which must be paid in Bitcoins.

The cost apparently depends on how quickly AUF's developers are contacted. They urge victims to contact them as soon as possible. As 'proof' that they can be trusted (are able to provide the decryption tool), they offer victims decryption one file free of charge.

They also urge them not to use any other tools/third party software, since, according to them, this might cause permanent data loss. They also state that none of the files should be renamed. We advise that you do not contact these cyber criminals or transfer any sums of cryptocurrency. Most cyber criminals ignore victims even if they receive payments.

They should never be trusted. Unfortunately, only they can provide a decryption tool, since most ransomware developers use cryptography algorithms (symmetric or asymmetric) that generate unique decryption keys. Therefore, no other tools are capable of decryption. Furthermore, cyber criminals store these keys on remote servers accessible only by them.

If your computer is infected with AUF, the only free option (at least, at time of writing) is to use a data backup and restore lost files from there.

Screenshot of a message encouraging users to pay a ransom to decrypt their compromised data:

AUF decrypt instructions

Most ransomware-type programs are very similar and serve the same purpose: to encrypt files and keep them in that state unless ransom demands are met. Some examples of other infections similar to AUF include PC-FunHACKED!, Paradise .xyz, and Rumba.

The main differences are usually cryptography algorithm used for encryption and cost of the tool required for decryption. Cyber criminals often design these ransomware-type programs to be 'uncrackable'. Therefore, decryption without the involvement of cyber criminals is impossible.

This might only be possible if the program is still in development or contains unfixed bugs/flaws. Therefore, maintain regular backups and keep them stored on remote servers or unplugged storage devices.

How did ransomware infect my computer?

It is not known exactly how cyber criminals proliferate AUF ransomware, however, these programs are usually distributed through spam (email) campaigns, trojans, Windows software cracks (and others), fake software updaters, and untrustworthy (dubious) software download sources.

Spam campaigns are used to proliferate computer infections by sending emails that include malicious attachments. These attachments might be Microsoft Office documents, PDF documents, archive files, executables, and so on. When opened, they infect computers by downloading and installing malicious programs.

Trojans, on the other hand, are programs (malicious) used to proliferate infections such as ransomware-type programs. If installed, they cause chain infections.

Untrustworthy software download sources such as P2P (peer-to-peer) networks (eMule, torrents clients and so on), freeware download websites, free file hosting site, third party software downloaders and so on, present malicious software as legitimate. Using these channels, people are often tricked into downloading and installing infections rather than the expected software.

Another way to proliferate ransomware and other threats are via fake software updaters. They are used to exploit bugs/flaws of outdated software or to download and install malicious programs rather than the promised software updates and fixes.

Threat Summary:
Name	AUF virus
Threat Type	Ransomware, Crypto Virus, Files locker
Symptoms	Can't open files stored on your computer, previously functional files now have a different extension, for example my.docx.locked. A ransom demanding message is displayed on your desktop. Cyber criminals are asking to pay 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?

To keep computers safe from various infections (including ransomware), be cautious while browsing the internet, downloading, installing and updating software. Various web links or attachments presented in emails received from unknown, suspicious or untrustworthy addresses should not be opened or clicked.

At least, ensure they are safe first. All software should be downloaded using official and trustworthy sources, and not third party downloaders, installers, or other channels of this type. These tools proliferate rogue applications that might cause computer infections or other unwanted installations.

Keep software updated, however, use implemented functions or tools provided by official developers, and not third party tools. Finally, have reputable anti-virus/anti-spyware software installed.

These tools can eliminate malware before any damage is done. If your computer is already infected with AUF, we recommend running a scan with Combo Cleaner Antivirus for Windows to automatically eliminate this ransomware.

Text presented in AUF ransomware pop-up window:

All your files have been encrypted!
All your files have been encrypted due to a security problem with your PC. If you want to restore them, write us to the e-mail Decisivekey@tutanota.com
Write this ID in the title of your message 1E857D00
In case of no answer in 24 hours write us to theese e-mails:Decisivekey@cock.li
You have to pay for decryption in Bitcoins. The price depends on how fast you write to us. After payment we will send you the decryption tool that will decrypt all your files.
Free decryption as guarantee
Before paying you can send us up to 1 file for free decryption. The total size of files must be less than 1Mb (non archived), and files should not contain valuable information. (databases,backups, large excel sheets, etc.)
How to obtain Bitcoins
The easiest way to buy bitcoins is LocalBitcoins site. You have to register, click 'Buy bitcoins', and select the seller by payment method and price.
https://localbitcoins.com/buy_bitcoins
Also you can find other places to buy Bitcoins and beginners guide here:
http://www.coindesk.com/information/how-can-i-buy-bitcoins/
Attention!
Do not rename encrypted files.
Do not try to decrypt your data using third party software, it may cause permanent data loss.
Decryption of your files with the help of third parties may cause increased price (they add their fee to our) or you can become a victim of a scam.

The appearance of AUF ransomware pop-up (GIF):

Screenshot of AUF text file:

AUF text file

Text presented in AUF ransomware text file:

all your data has been locked us
You want to return?
write email Decisivekey@tutanota.com or Decisivekey@cock.li

Screenshot of files encrypted by AUF (".AUF" extension, which also contains a unique ID and the developer's email address):

Files encrypted by AUF

AUF ransomware removal:

Instant automatic malware removal:

Manual threat removal might be a lengthy and complicated process that requires advanced IT skills. Combo Cleaner is a professional automatic malware removal tool that is recommended to get rid of malware. Download it by clicking the button below:

DOWNLOAD Combo Cleaner

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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.

Microsoft Defender Offline Free · built-in

Built into Windows. Scans before Windows fully loads to catch persistence the running scanners miss.

Microsoft Safety Scanner (MSERT) Free

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.

No More Ransom Project Free · web

Joint project of Europol, Dutch Police, and security vendors. Free decryption tools indexed by ransomware family.

Shadow Explorer Free

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

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.

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.

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

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.

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.

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.

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

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

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.

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

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

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.

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

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

Canada: antifraudcentre.ca

Australia: ReportCyber

Spain: Policía Nacional (Oficina Virtual de Denuncias)

France: cybermalveillance.gouv.fr

Germany: BKA

Italy: Polizia Postale

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.

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.

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.