Avaddon (.avdn) ransomware virus - removal and decryption options

What kind of malware is Avaddon?

This ransomware was discovered by GrujaRS. Avaddon encrypts files with the AES encryption algorithm and encrypts an AES key using the RSA algorithm. It also changes the desktop wallpaper and renames all files by appending the ".avdn" extension. For example, it renames a file named "1.jpg" to "1.jpg.avdn", "2.jpg" to "2.jpg.avdn", and so on.

Instructions about how to access the website, which victims must supposed use to pay the ransom, are provided in the "[random_numbers]-readme.html" file. Avaddon drops this file in every folder that contains encrypted files.

Screenshot of files encrypted by Avaddon (".avdn" extension):

Ransom note overview

The ransom message within the HTML file states that Avaddon encrypts documents, photos, databases and other important files, and that it is impossible to decrypt them without software called "Avaddon General Decryptor".

Victims can apparently purchase this decryption tool by following the instructions provided on a Tor website, which contains information such as cost of the aforementioned decryption tool, how much time victims have to purchase it until the cost is doubled, and various other details.

It is stated that decryption software costs the equivalent of 0.05346968 Bitcoin and must be purchased by transferring this BTC amount to the provided address (BTC wallet). If victims make not purchase within 7 days and 12 hours, the cost is doubled. Victims supposedly receive the Avaddon General Decryptor after the transaction is made and the payment is confirmed.

More about ransomware

You are strongly advised not to pay any ransom to these cyber criminals - it is very likely that they will not send any decryption tool, even if you meet all of their demands. Unfortunately, there are no free tools that can decrypt files compromised by this ransomware (only the developers have valid decryption tools).

In such cases, victims can avoid data loss by restoring files from a backup. It is possible to prevent further encryption of unaffected files by uninstalling ransomware from the computer, however, already compromised files remain encrypted even when the malware is no longer installed on the operating system.

Malware such as Avaddon encrypt files so they cannot be recovered without specific software and/or a decryption key. Some examples of other ransomware programs are Kkll, Professeur and PGP. Main differences are size of ransom and encryption algorithm that ransomware uses to encrypt data.

Only the cyber criminals behind ransomware have tools that can recover files that were encrypted by it, unless in rare cases the ransomware is not finished (contains bugs, flaws). Therefore, you are advised to have data backed up on a remote server or unplugged storage device.

How did ransomware infect my computer?

Users often infect their computers inadvertently with malware (including ransomware) through malspam campaigns, unofficial software activators and updaters, dubious file and software download channels and Trojans. Cyber criminals use spam campaigns to proliferate malware by sending emails with malicious attachments or website links that download malicious files.

They attempt to trick people into executing a malicious file by disguising their emails as important, official and legitimate. When recipients open the malicious file, however, they cause installation of malware.

Examples of files that cyber criminals attach to their emails are malicious Microsoft Office documents, executable files (.exe), JavaScript files, PDF documents, archive files (ZIP, RAR). Users also infect computers when they use various unofficial, third party activation tools to activate licensed software.

These tools supposedly bypass activation free of charge, however, they often install malware instead. The same applies to third party updaters - rather than updating any software, they install malicious programs. They also exploit bugs/flaws of installed software that is out of date.

Malicious software is also distributed through dubious download channels. For example, third party downloaders, unofficial websites, Peer-to-Peer networks (torrent clients, eMule), freeware download sites, free file hosting pages, etc. Systems become infected when users open/execute malicious files that were downloaded through such channels.

Note that the rogue files are often disguised as regular and legitimate. Trojans are malicious programs that distribute malware and cause chain infections, however, they can only install additional malware they are already installed onto the user's computer.

How to protect yourself from ransomware infections

All software should be downloaded only from official, trustworthy websites and direct links. Third party downloaders, installers and other channels (mentioned above) are often used to proliferate malware. Installed software must be updated and activated (if necessary) through tools/functions that are designed by the official developers.

Unofficial, third party updating and activation tools should never be used. Note that it is illegal to activate licensed programs with 'cracking' tools (third party activators). Do not open attachments or links in irrelevant emails that are received from suspicious, unknown addresses.

Open email contents when there is no doubt about safety. Regularly scan the operating system for threats with reputable antivirus or anti-spyware software. Keep this software up to date. If your computer is already infected with Avaddon, we recommend running a scan with Combo Cleaner Antivirus for Windows to automatically eliminate this ransomware.

Appearance of "[random_numbers]-readme.html" file (GIF):

Text in this HTML file:

Your network has been infected by Avaddon
All your documents, photos, databases and other important files have been encrypted and you are not able to decrypt it by yourself. But don't worry, we can help you to restore all your files!

 

The only way to restore your files is to buy our special software - Avaddon General Decryptor. Only we can give you this software and only we can restore your files!

 

You can get more information on our page, which is located in a Tor hidden network.

 

How to get to our page
Download Tor browser - hxxps://www.torproject.org/
Install Tor browser
Open link in Tor browser - avaddonbotrxmuyl.onion
Follow the instructions on this page
Your ID:
-

 

DO NOT TRY TO RECOVER FILES YOURSELF!

DO NOT MODIFY ENCRYPTED FILES!

OTHERWISE, YOU MAY LOSE ALL YOUR FILES FOREVER!

Screenshot of the HTML file:

Appearance of the Avaddon Tor website (GIF):

Text in this website:

Brand
Your network has been infected by Avaddon

 

Don't worry, we can help you to restore all your files!

 

Avaddon General Decryptor price is 500 USD* 7:11:58:31
*If you don’t pay before the time runs out, the price will be doubled!

 

All your documents, photos, databases and other important files have been encrypted!

 

To restore all your files you need to buy our special software - Avaddon General Decryptor!

 

You can do it right now. Follow the instruction below. But remember that you do not have much time!
500 USD
≈ 0.05346968 BTC
3JtU8efLk6c176nnntDYCTyBg9biuSdKiE
NOT PAID

 

1. Buy the Bitcoin cryptocurrency. You will find instructions how you can do it below.

 

2. Send 0.05346968 BTC to the address: 3JtU8efLk6c176nnntDYCTyBg9biuSdKiE (in ONE payment, this amount doesn’t include the transaction fee)

 

3. The transaction will be confirmed after receiving 6 confirmations

 

4. When the payment is confirmed, you can download the Avaddon General Decryptor.
Attention!

 

Please be careful and visually check the address after copy-paste (because on your PC there is probably a malware monitoring and changing the address in your clipboard)

 

How to buy Bitcoin

- Buy Bitcoin from a bank account or by bank transfer
Coinmama, Bitpanda, Coinfloor, Kraken, Coinfinity, BTC Direct, Change Invest, Coinbase, EXMO, CEX.IO, Bitfinex, Bitstamp, Gemini, Lykke, BTCBIT

- Buy Bitcoin through PayPal
Etoro, Local Bitcoins

- Buy Bitcoin with a Credit/Debit Card
Changelly, Bitpanda, Bitstamp, Coinbase, EXMO, CEX.IO, Lykke, BTCBIT, Change now

- Buy bitcoin in cash or cash deposit
Local Bitcoins, Bitquick, Libertyx, Bit it, Bitcoin ATMs, Bitcoin ATM Radar

Screenshot of Avaddon desktop wallpaper:

Screenshot of Avaddon malicious process running in Task Manager as "237502353.exe" (its name might vary):

Update 10 June 2020 - Cyber criminals have recently started an email spam campaign to spread Avaddon ransomware. The text within the email is a smile: ";)". The email subject, however, is "Your new photo?" and also contains an archive file attached ("IMG159131.jpg.js.zip").

The archive contains a JavaScript file named "IMG159131.jpg". For users who do not have the "display file extensions" option enabled, the file may seem to be an ordinary image (.jpg format), however, this is a script designed to download and execute Avaddon ransomware.

Screenshot of the spam email:

Screenshot of a website displayed after paying the ransom to Avaddon's developers. Note that paying does not guarantee that your files will be decrypted (in most cases, criminals scam the victims and paying gives no benefit):

Update 26 June 2020 - One victim has confirmed that paying gives no value - the Download button for the decryption tool does not work and simply leads to a nonexistent web page:

Update 1 July 2020 - A new variant of Avaddon ransomware has been discovered. This variant drops a different ransom message, sets a different desktop wallpaper and adds a random file extension.

Screenshot of this variant's ransom message:

Text presented within:

Your network has been infected!
All your documents, photos, databases and other important files have been encrypted and you are not able to decrypt it by yourself. But don't worry, we can help you to restore all your files!

The only way to restore your files is to buy our special software. Only we can give you this software and only we can restore your files!

You can get more information on our page, which is located in a Tor hidden network.

How to get to our page
Download Tor browser - hxxps://www.torproject.org/
Install Tor browser
Open link in Tor browser - ZY010ndXea30XMmPb5s.avaddonbotrxmuyl.onion/?AdYOgB3ONcK
Follow the instructions on this page
Your ID:
-
DO NOT TRY TO RECOVER FILES YOURSELF!

DO NOT MODIFY ENCRYPTED FILES!

OTHERWISE, YOU MAY LOSE ALL YOUR FILES FOREVER!

atM3v99uMHyfEjFPIYgyCvf

Screenshot of this variant's desktop wallpaper:

Text presented within:

Files are encrypted
If you do not pay, YOU WILL LOSE ALL FILES FOREVER!

Find: Hl_readme.html
in folders or on your desktop!

You have a few days TO PAY or
ALL INFORMATION ABOUT YOU
WILL BE PUBLISHED IN PUBLIC ACCESS !!!

Screenshot of files encrypted by this variant (random extension):

Example of a ransom message ("G_readme.html") delivered by yet another Avaddon ransomware variant:

Text presented within:

Your network has been infected!
Your files are locked due to a vulnerability in your system

You will not be able to decrypt the files yourself, in the worst case you can destroy the data irreversibly.

The only way to unlock your data is to buy the decryption program.

Go to the link written below to more details.

If you do not pay for recovery, then all the confidential data from your computer WILL BE TRANSFERRED TO PUBLIC ACCESS. Follow the instructions below to restore your files and keep them confidential.

If you cannot do this yourself, find a data recovery company in internet.

They cannot help you unlock your data, because only we have decryption key, but will help you make a payment and provide you guarantees.

ATTENTION! DATA RECOVERY AGENCIES WORK AND DURING THE CORONOVIRUS QUARANTINE, THEY WILL HELP YOU REMOTE.

Also, I ask you to note, you have no long time, if you do not make payment soon, the price for the decryptor will double. So I recommend you dont waste time and move!

How to get to our page
Download Tor browser - hxxps://www.torproject.org/
Install Tor browser
Open link in Tor browser - zcQ3LA.avaddonbotrxmuyl.onion/?5JM0UXN905lovYAeikPgkwa9nY
Follow the instructions on this page
Your ID:
-

DO NOT MODIFY ENCRYPTED FILES!

OTHERWISE, YOU MAY LOSE ALL YOUR FILES FOREVER!

Yet another variant of a ransom note delivered by Avaddon ransomware:

Text presented within:

-------===    Your network has been infected!    ===-------

*****************    DO NOT DELETE THIS FILE UNTIL ALL YOUR DATA HAVE BEEN RECOVERED    *****************

All your documents, photos, databases and other important files have been encrypted and have the extension: .beEdeCDAea

You are not able to decrypt it by yourself. But don't worry, we can help you to restore all your files!

The only way to restore your files is to buy our special software. Only we can give you this software and only we can restore your files!
We have also downloaded a lot of private data from your network.

If you do not contact as in a 3 days we will post information about your breach on our public news website and after 7 days the whole downloaded info.

You can get more information on our page, which is located in a Tor hidden network.

How to get to our page

----------------------

|

|  1. Download Tor browser - hxxps://www.torproject.org/

|

|  2. Install Tor browser

|

|  3. Open link in Tor browser - avaddonbotrxmuyl.onion

|

|  4. Follow the instructions on this page

|

----------------------

Your ID:

----------------------
-
----------------------
* DO NOT TRY TO RECOVER FILES YOURSELF!
* DO NOT MODIFY ENCRYPTED FILES!
* * * OTHERWISE, YOU MAY LOSE ALL YOUR FILES FOREVER! * * *
9M

Update February 9, 2021 - Javier Yuste has recently shared a GitHub page providing an open-source decryptor for Avaddon ransomware. The decryption process is rather simple. You can download the tool and find its manual in Javier Yuste's GitHub page.

Update June 14, 2021 - Cyber criminals have closed the Avaddon ransomware operation and released all the decryption keys. This allowed Emsisoft team to develop a decryption tool (download link) capable of restoring data compromised by Avaddon ransomware.

Screenshot of Emsisoft's Avaddon decryptor:

Update June 06, 22 - Bitdefender has also released a decryption tool for Avaddon ransomware (download link and user manual).

Screenshot of Bitdefender's decryption tool for Avaddon ransomware:

Avaddon 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.

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.

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.

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.

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.

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

---

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.

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.

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.

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.

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

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.

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?

It is known that cybercriminals distribute Avaddon ransomware via email - they send emails containing malicious attachments. In other cases, ransomware can encrypt data via files downloaded from unreliable sources, installers for pirated software (or cracking tools), fake software updating tools, Trojans, drive-by downloads, etc.

How to open ".avdn" files?

These files cannot be opened until they are decrypted.

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

Files encrypted by Avaddon ransomware can be decrypted with a tool created by Emsisoft of Bitdefender.

Should I pay cybercriminals a ransom?

Not all threat actors provide decryption tools after the payment. Thus, it is strongly recommended not to trust (pay) them.

Will Combo Cleaner help me remove Avaddon ransomware?

Yes, Combo Cleaner will remove ransomware from the infected computer. It should be removed to prevent more data loss. Files remain encrypted even after the removal. Antivirus software does not decrypt encrypted files.