IIOF ransomware is a new variant of STOP/DJVU file-encrypting malware
Contents
IIOF ransomware is a malicious virus that functions by encrypting files found in any computer it infects. It is recognized as a member of the notorious and highly destructive STOP/DJVU ransomware family. It is known to encrypt every file it can locate in the compromised computer and would append each of them with .iiof extension. E.g., a file that was hitherto known as 1.jpg will be automatically renamed 1.jpg.iiof and the same modifications will be applied to all affected files. Simultaneously, it will equally drop certain ransom notifications called _readme.txt in all the folders. These notifications are basically information from the cybercriminals explaining what has happened and how/the need for the victim to get in touch with them in view of paying ransom to enable them to receive IIOF decryption tool.
In the ransom note, they will point out that IIOF ransomware virus has successfully encrypted every single file contained in the victim’s computer, including potentially vital documents, pictures, and every other data using a very complex key. As a result, they have no other choice than to pay the ransom fee being requested so they could forward a decryption key accordingly. Additionally, the message will contain two email addresses namely: support@sysmail.ch and helprestoremanager@airmail.cc which they hope the victim will use in responding to them.
They will also attach decryption service prices and the terms of payment associated with them. For instance, they will claim that responding ASAP to their demand would be beneficial. Such that, if the victim is able to respond in the next 72 hours/3 days, they would be able to leverage their 50% discount. Therefore, instead of paying a fee of $980, they would now pay $490. However, once the 3 days window closes, only the full amount would be acceptable.

If the victim decides to reach out to them, the cybercriminals will give further conditions by requesting that payment can only be made by purchasing cryptocurrency that is worth the ransom fee and transferring same to a wallet address that would be provided by them. The apparent reason why they use this medium of payment is to remain anonymous and evade possible arrests by law enforcement agencies. To raise the hopes of the victim and encourage them to pay without hesitation, they sometimes ask for excerpts of the encrypted files to be sent to them so they could decrypt it as proof of their expertise.
However, our cybersecurity experts advise that victims should follow the FBI’s directive in respect to ransom demand and the verdict is NO TO RANSOM PAYMENT. It should be noted that paying the ransom does not guarantee the victim will recover their encrypted data. On the contrary, you will end up encouraging cybercriminals to continue in their criminal activities since they would find it profitable.
Annually, these online rogues earn millions of dollars from victims whose files were encrypted and this is bad. In addition to that, the virus is also known for dropping Trojans that steal information such as AZORULT and VIDAR on the already compromised PC which they use in stealing confidential information like software account login details, cryptocurrency wallets, banking details, passwords etc. and such sensitive information in the wrong hands can result in further criminal activities like money pilfering or blackmail.
For those who unfortunately became victims of the described variant of STOP/DJVU virus, you’re advised to remove IIOF ransomware from your PC as quickly as possible. The recommended way to do it is to set up your PC in Safe Mode with Networking option while it is still booting before running any reliable antivirus software. If you’re not sure about which antivirus would be most suitable, then you should make use of INTEGO Antivirus. In addition to that, you can also download RESTORO to help in repairing possible virus damages on your Windows OS files.
Ransomware Summary
Name | IIOF Ransomware Virus |
Type | Ransomware; Crypto-malware; Virtual Extortion Virus |
Family | STOP/DJVU |
Encryption type | RSA 2048 + Salsa20 |
Previous versions | JYPO, KIFR, KIOP, KITZ, BOZA, BOTY, COZA (find full list here) |
Version | 410th |
Extension | .iiof |
Cybercriminal emails | support@sysmail.ch, helprestoremanager@airmail.cc |
Additional malware dropped | Azorult or Vidar Trojan |
Damage | The ransomware encrypts files and adds .iiof extension after the original file extension. Then this virus drops _readme.txt ransom note in every folder. Moreover, the malware drags VIDAR Stealer into the compromised computer. Additionally, the ransomware may also delete Volume Shadow Copies and modify Windows HOSTS file to restrict computer user’s access to cybersecurity-related websites online. |
Ransom note | _readme.txt |
Ransom demand | $490-$980 in Bitcoin |
Distribution | Victims often download this ransomware along illegal torrent downloads, cracked software, activators, key generators or tools like KMSPico. |
Known software cracks to contain this malware | Corel Draw, Tenorshare 4ukey, Adobe Photoshop, Cubase, Adobe Illustrator, Internet Download Manager, Tally, League of Legends. |
Detection names | Ransom:Win32/StopCrypt.PAL!MTB (Microsoft), Trojan.Crypt (A) (Emsisoft), HEUR:Trojan-Ransom.Win32.Stop.gen (Kaspersky), Trojan.GenericKD.47850419 (BitDefender), Trojan.MalPack.GS (Malwarebytes), ML.Attribute.HighConfidence (Symantec) see all detection name variations on VirusTotal |
Removal | Remove ransomware and related malware from your PC using professional software of your choice. We highly recommend using INTEGO Antivirus. To repair virus damage on Windows OS files, consider scanning with RESTORO. |
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Ransomware distribution techniques used by cybercriminals
Basically, the most common method used by cybercriminals in spreading different variants of STOP/DJVU ransomware, including IIOF virus, is through malicious online torrents whereby they would hibernate malware in certain types of pirated software contents such as the so-called “cracks” or fake key generators. When unsuspecting users try to make use of these illegal software contents they end up triggering malware attack on their computer. Such illegal software contents used as bait by cybercriminals are then uploaded to diverse online torrent libraries:
- Internet Download Manager;
- Corel Draw;
- Tenorshare 4ukey;
- AutoCad;
- Opera browser;
- Fifa 20;
- VMware Workstation;
- Cubase;
- Virtual DJ Pro;
- League of Legends;
- Adobe Photoshop;
- KMSPico (illegal Windows activation tool).
Based on the explanations so far, it has been shown that going to online torrents to download any type of software is a dangerous habit, and anyone involved in it should desist from doing so to avoid becoming a victim of a cyberattack. Furthermore, it is a copyright offence to do so and is punishable by law. A better alternative is to download such software needs through the right channels, thereby encouraging legitimate software developers. Although it may seem like the fees charged by software developers are high relative to online torrents platforms but when you consider the outrageous amount of money victims of ransomware are asked to pay, you will realize it’s not worth it. Also, using the right channels poses no risk to your sensitive personal data.
Another method used by cybercriminals in spreading malware is through malicious email attachments. In this case, they would create highly convincing messages while attaching certain types of documents crafted on PDF, DOCX or XLS among similar files. They use these particular files because they allow JavaScript and macro functions which can be used to transport and trigger payload in diverse random computers.
The most worrisome part of it is that trying to decipher if a particular email is coming from a genuine source or a malware carrying medium sent by cybercriminals has become increasingly difficult. The reason is because cybercriminals now pretend to be acquaintances or maybe any popular brand (the ones often used include Amazon, UPS, eBay, or DHL, among others. Also, they tend to give the accompanying attachments compelling names like Tracking Details, Invoice or Order Summary etc. Alternatively, cybercriminals make use of email spoofing techniques which they use in obfuscating the actual originating email address. In such circumstances, it is best to trust your intuition and avoid opening any email that appears odd.
Lastly, STOP/DJVU ransomware victims should avoid certain dubious websites that claim to offer miraculous decryption solutions because they’re actually scammers with ulterior motives. At the moment, only Emsisoft and DiskTuna have proven to offer decryption solutions that actually work. Here is a link to them. Nevertheless, you should be aware that cybercriminals equally distribute other versions of ransomware like ZORAB through certain types of fake STOP/DJVU decryptors. Any attempt to download such tools can automatically lead to double-file encryption.
More details concerning the infection
Those that may be wondering about the extent of damage that was done on their PC following XXXX ransomware attack should avail themselves of the information contained in this section. Firstly, what the malware does is to launch build.exe or build2.exe executables as well as winupdate.exe. Afterwards, it would make a connection with https[:]//api.2ip.ua/geo.json and afterwards, saves the result to geo.json file. The malware then commences with information gathering of all details concerning the computer and would store them in geolocation related database; this would include the computer’s geolocation information, zip code, time zone, latitude and longitude. Please check below for a derived example of geo.json file.

Another file would be created that would contain hardware details, software list, and active processes sent to information.txt.

Afterwards, the malware will profile the country code it earlier extracted and would compare it against their list of encryption exempted countries, namely; Russian Federation, Belarus, Syria, Armenia, Ukraine, Kazachstan, Tajikistan, Kyrgyzstan, and Uzbekistan. In a situation where the virus detects one of the listed countries, it would immediately cease any further attempt to encrypt data on the computer. However, if the computer’s location doesn’t fall into the whitelist, it will then extract online encryption key from the C&C server and would combine it with the victim’s ID before saving them in bowsakkdestx.txt file and also to PersonalID.txt file. Both files are portrayed in the image below.

However, if it fails to extract any online encryption key from the central server, it will settle for the use of a hardcoded offline key. The main difference between the two is that online key is unique for each victim, unlike offline key that is used for all victims of a particular ransomware variant. What shows that offline key was used is the availability of t1 characters appearing at the end of a personal ID, and the implication is that there is a high chance that such victim could decrypt .iiof files someday. More details about this are provided below the article.
At this juncture, the ransomware will commence full data encryption procedure by scanning every folder and encrypting them with Salsa20 before locking the key using RSA-2048. While the process is still going on, the virus will mark each file name with .iiof extension.

Here is a screenshot of the _readme.txt ransom note that is usually left in all the folders.

Ultimately, the virus will proceed to delete Volume Shadow Copies by making use of the command task as shown below:
vssadmin.exe Delete Shadows /All /Quiet
Thereafter, it would add certain domains to the Windows HOSTS file before mapping them to localhost IP, thereby effectively preempting any possible attempt by the victim to seek help from those blacklisted websites. Any attempt by the victim could bring up the DNS_PROBE_FINISHED_NXDOMAIN error message. The reason why they do this is to ensure that victims are totally helpless and confused on what to do.
Remove IIOF Ransomware Virus and Recover lost files
Victims whose files were encrypted by this malware variant should remove IIOF ransomware virus as quickly as possible and also endeavor to report to the appropriate government agency entrusted to handle such issues. However, the guide below shows how you can easily set up your PC in Safe Mode with Networking option (highly recommended) before running genuine antivirus software on it. For those that are not of which antivirus to use, consider using INTEGO Antivirus because it has been tested by our team and found to be very efficient.
Once IIOF ransomware virus removal is done, please take the following steps:
- Inform a relevant law enforcement agency near to you.
- Make use of any data backup device to restore lost files.
- Learn possible ways files affected by STOP/DJVU ransomware versions can be decrypted.
- Change all passwords that were used on the infected computer.
- Download RESTORO and run a system scan to identify and repair virus damage to Windows OS files.
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IIOF Ransomware Virus Removal Guidelines
Method 1. Enter Safe Mode with Networking
Step 1. Start Windows in Safe Mode with Networking
Before you try to remove IIOF Ransomware Virus virus, you must start your computer in Safe Mode with Networking. Below, we provide the easiest ways to boot PC in the said mode, but you can find additional ones in this in-depth tutorial on our website – How to Start Windows in Safe Mode. Also, if you prefer a video version of the tutorial, check our guide How to Start Windows in Safe Mode on Youtube.
Instructions for Windows XP/Vista/7 users
- First of all, turn off your PC. Then press the Power button to start it again and instantly start pressing F8 button on your keyboard repeatedly in 1-second intervals. This launches the Advanced Boot Options menu.
- Use arrow keys on the keyboard to navigate down to Safe Mode with Networking option and press Enter.
Instructions for Windows 8/8.1/10/11 users
- Open Windows Start menu, then press down the Power button. On your keyboard, press down and hold the Shift key, and then select Restart option.
- This will take you to Windows Troubleshoot screen. Choose Troubleshoot > Advanced Options > Startup Settings > Restart. Tip: If you can't find Startup Settings, click See more recovery options.
- In Startup Settings, press the right key between F1-F9 to enter Safe Mode with Networking. In this case, it is the F5 key.
Step 2. Remove files associated with the virus
Now, you can search for and remove IIOF Ransomware Virus files. It is very hard to identify files and registry keys that belong to the ransomware virus, Besides, malware creators tend to rename and change them repeatedly. Therefore, the easiest way to uninstall such type of a computer virus is to use a reliable security program such as INTEGO Antivirus. For virus damage repair, consider using RESTORO.
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Method 2. Use System Restore
In order to use System Restore, you must have a system restore point, created either manually or automatically.
Step 1. Boot Windows in Safe Mode with Command Prompt
Instructions for Windows XP/Vista/7 users
- Shut down your PC. Start it again by pressing the Power button and instantly start pressing F8 button on your keyboard repeatedly in 1-second intervals. You will see Advanced Boot Options menu.
- Using arrow keys on the keyboard, navigate down to Safe Mode with Command Prompt option and press Enter.
Instructions for Windows 8/8.1/10/11 users
- Launch Windows Start menu, then click the Power button. On your keyboard, press down and hold the Shift key, and then choose Restart option with the mouse cursor.
- This will take you to Windows Troubleshoot screen. Choose Troubleshoot > Advanced Options > Startup Settings > Restart. Tip: If you can't find Startup Settings, click See more recovery options.
- In Startup Settings, press the right key between F1-F9 to enter Safe Mode with Command Prompt. In this case, press F6 key.
Step 2. Start System Restore process
- Wait until system loads and command prompt shows up.
- Type cd restore and press Enter, then type rstrui.exe and press Enter. Or you can just type %systemroot%system32restorerstrui.exe in command prompt and hit Enter.
- This launches System Restore window. Click Next and then choose a System Restore point created in the past. Choose one that was created before ransomware infection.
- Click Yes to begin the system restoration process.
After restoring the system, we recommend scanning the system with antivirus or anti-malware software. In most cases, there won't be any malware remains, but it never hurts to double-check. In addition, we highly recommend checking ransomware prevention guidelines provided by our experts in order to protect your PC against similar viruses in the future.
Alternative software recommendations
Malwarebytes Anti-Malware
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Decrypt IIOF files
Fix and open large IIOF files easily:
It is reported that STOP/DJVU ransomware versions encrypt only the beginning 150 KB of each file to ensure that the virus manages to affect all files on the system. In some cases, the malicious program might skip some files at all. That said, we recommend testing this method on several big (>1GB) files first.
- Create a copy of encrypted file to a separate folder using Copy > Paste commands.
- Now, right-click the created copy and choose Rename. Select the IIOF extension and delete it. Press Enter to save changes.
- In the prompt asking whether you want to make the changes as file might become unusable, click OK.
- Try opening the file.
STOP/DJVU decryption tool usage guide
STOP/DJVU ransomware versions are grouped into old and new variants. IIOF Ransomware Virus is considered the new STOP/DJVU variant, just like JYPO, KIFR, KIOP, KITZ, BOZA, BOTY, COZA (find full list here). This means full data decryption is now possible only if you have been affected by offline encryption key. To decrypt your files, you will have to download Emsisoft Decryptor for STOP DJVU, a tool created and maintained by a genius security researcher Michael Gillespie.
Note! Please do not spam the security researcher with questions whether he can recover your files encrypted with online key - it is not possible.
In order to test the tool and see if it can decrypt IIOF files, follow the given tutorial.
- Download the decryption tool from Emsisoft.
- Click the little arrow next to your download and choose Show in Folder.
- Now, right-click the file and choose Run as Administrator. If asked, enter administrator's password.
- In UAC window, click Yes.
- Click Yes to agree to software terms in both windows.
- The tool will automatically include C:// disk as a location to decrypt. The file recovery tool will prepopulate the locations to scan, including connected data storage drives or network drives. Click Add folder if you wish to add additional locations.
In Options tab, you can choose to keep encrypted file copies. We recommend leaving this option selected, especially if you do not know if the decryption tool will work. - Click Decrypt to start restoring IIOF files. You will see the progress in the Results tab. Here, you can see messages from the tool, such as whether the decryption procedure is successful, or you need to wait for an update.
You might also be informed that online key was used to encrypt your files. In such case, the decryption tool won't work for you, and the only way to recover your files is to use a data backup.
Meanings of decryptor's messages
The IIOF decryption tool might display several different messages after failed attempt to restore your files. You might receive one of the following messages:
Error: Unable to decrypt file with ID: [example ID]
This message typically means that there is no corresponding decryption key in the decryptor's database.
No key for New Variant online ID: [example ID]
Notice: this ID appears to be an online ID, decryption is impossible
This message informs that your files were encrypted with online key, meaning no one else has the same encryption/decryption key pair, therefore data recovery without paying the criminals is impossible.
Result: No key for new variant offline ID: [example ID]
This ID appears to be an offline ID. Decryption may be possible in the future.
If you were informed that an offline key was used, but files could not be restored, it means that the offline decryption key isn't available yet. However, receiving this message is extremely good news, meaning that it might be possible to restore your IIOF extension files in the future. It can take a few months until the decryption key gets found and uploaded to the decryptor. We recommend you to follow updates regarding the decryptable DJVU versions here. We strongly recommend backing up your encrypted data and waiting.
Report Internet crime to legal departments
Victims of IIOF Ransomware Virus should report the Internet crime incident to the official government fraud and scam website according to their country:
- In the United States, go to the On Guard Online website.
- In Australia, go to the SCAMwatch website.
- In Germany, go to the Bundesamt für Sicherheit in der Informationstechnik website.
- In Ireland, go to the An Garda Síochána website.
- In New Zealand, go to the Consumer Affairs Scams website.
- In the United Kingdom, go to the Action Fraud website.
- In Canada, go to the Canadian Anti-Fraud Centre.
- In India, go to Indian National Cybercrime Reporting Portal.
- In France, go to the Agence nationale de la sécurité des systèmes d’information.
If you can't find an authority corresponding to your location on this list, we recommend using any search engine to look up "[your country name] report cyber crime". This should lead you to the right authority website. We also recommend staying away from third-party crime report services that are often paid. It costs nothing to report Internet crime to official authorities.
Another recommendation is to contact your country's or region’s federal police or communications authority.
Frequently Asked Questions
You can only open IIOF files if you have the decryption key, or if you were affected by offline encryption type.
To figure out whether you were affected by offline encryption, please go to C:/SystemID/PersonalID.txt and see if the string inside of it ends in t1. You can also try using Emsisoft Decryptor for STOP/DJVU.
Please follow the guidances provided by the official IIOF decryption tools and believe what they say. If they say it is impossible to decrypt, it really is so. There is no magic tool or human capable of decrypting your files hiding somewhere. Encryption is a technique created to be nearly impossible to decrypt without a special private key (held by the criminals).
We advise scanning with anti-virus, anti-malware, malware removal tools or software like RESTORO to eliminate virus damage on the system. If you do not trust using a single tool, try running one after another. However, we do not recommend keeping several security programs on a computer at once as they can interfere with each other's work.
Beware of fake IIOF decryption tools circulating around the web. Cyber criminals are uploading them to various shady websites, also might be promoting them via suspicious Youtube videos. These programs can infect your computer even more heavily (Trojans, miners, etc.). We suggest being extremely cautious around the web. If there will be an official STOP/DJVU decryption tool available, it will be widely discussed in public media.

Norbert Webb is the head of Geek’s Advice team. He is the chief editor of the website who controls the quality of content published. The man also loves reading cybersecurity news, testing new software and sharing his insights on them. Norbert says that following his passion for information technology was one of the best decisions he has ever made. “I don’t feel like working while I’m doing something I love.” However, the geek has other interests, such as snowboarding and traveling.
I need help decrypting iiof files.