Trojan:Win32/Leonem!rfn – Removal Guide [Working]

What is Trojan:Win32/Leonem!rfn?

Microsoft Defender flagged Trojan:Win32/Leonem!rfn on your system and you want to know whether this is a real infection or a false positive, and exactly what to do about it. Read this guide carefully before clicking anything in Defender or deleting files manually.

Trojan:Win32/Leonem!rfn is a Microsoft Defender detection for credential-stealing spyware. The Leonem family is described by Microsoft’s own threat database as detection for a broad selection of malware united by the presence of spyware capabilities. The !rfn suffix indicates the detection is based on behavioral or reputation analysis rather than an exact signature match, which means the threat may be real without being an exact known sample – and also means there is a small possibility of a false positive against a legitimate file exhibiting similar behavioral patterns. When the detection is real, Leonem differs from standard infostealers through its dual functionality: it extracts authentication data from the system while also being capable of downloading and executing additional malware. Gridinsoft describes it as targeting credentials, session tokens, and login data from browsers and email clients. SpyHunter is confirmed to successfully detect and remove Trojan:Win32/Leonem!rfn.

How Did I Get Trojan:Win32/Leonem!rfn?

When the detection is confirmed malicious, the infection arrives through these documented routes:

• An unofficial download path such as a bundled installer or fake update – The most documented delivery route: a free program from a third-party site, a cracked application, or a fake browser/software update page delivers the Trojan alongside or instead of the claimed content through software bundling.
• Modified game files and pirated software – Game mods, cracks, and pirated application installers downloaded from unofficial sources are a consistent delivery vehicle for Trojans in the Leonem family.
• Malicious email attachments – A document or archive received through a spam email executes a dropper that installs the Trojan on the system when opened.
• Drive-by downloads from compromised pages – Visiting a compromised or ad-heavy page can silently download and execute the Trojan installer without any explicit user action.

What Does Trojan:Win32/Leonem!rfn Do?

When confirmed real, the threat operates on multiple simultaneous tracks. Here is the full picture:

• Steals credentials, session tokens, and login data – The primary documented function of the Leonem family is credential extraction from browsers and email clients – saved passwords, session cookies, autofill data, and account login details are harvested and transmitted to the attacker’s infrastructure.
• Downloads and installs additional malware – The dual-functionality architecture means Leonem often functions as a dropper or foothold for further payloads. A Leonem detection is rarely the complete picture of the infection – additional components may have been installed alongside it.
• Records keystrokes and visited sites – As a spyware component, the Trojan can log keyboard input and browsing activity, capturing credentials entered manually even if they were not saved in the browser.
• Gives remote access to the attacker – Some variants in this detection family include backdoor functionality, allowing the attacker to remotely access, modify, or further compromise the infected system.

False positive check: If the detection points to a known, signed application from a reputable developer and the file path matches the expected software installation directory, submit the file to VirusTotal. If fewer than three engines flag it and the file is signed by a known publisher, a false positive is more likely. If the file is unsigned, located in AppData or Temp, or arrived through an unofficial download, treat it as real.

What Should You Do?

Do not click Allow or Restore in Defender – quarantine the file immediately. Update Defender to the latest definitions and run a full offline scan (Windows Security, then Virus and Threat Protection, then Scan Options, then Microsoft Defender Offline Scan). If the alert keeps returning, check Task Scheduler for any task pointing to an unfamiliar script or path, and check the Startup tab in Task Manager for any entry tied to the alert. If a login exposure is possible – meaning the Trojan was active for any period before detection – change all passwords from a completely clean device and enable 2FA on all accounts before using any of them from the affected machine. Run a full scan with a dedicated anti-malware tool to catch any additional components that Defender may have missed. SpyHunter is confirmed to successfully remove Trojan:Win32/Leonem!rfn. Follow the complete removal guide below this article for the full step-by-step process.

Ventsislav Krastev

Ventsislav is a cybersecurity expert at SensorsTechForum since 2015. He has been researching, covering, helping victims with the latest malware infections plus testing and reviewing software and the newest tech developments. Having graduated Marketing as well, Ventsislav also has passion for learning new shifts and innovations in cybersecurity that become game changers. After studying Value Chain Management, Network Administration and Computer Administration of System Applications, he found his true calling within the cybersecrurity industry and is a strong believer in the education of every user towards online safety and security.

More Posts - Website

Follow Me:

---

Preparation before removing Trojan:Win32/Leonem!rfn.

Before starting the actual removal process, we recommend that you do the following preparation steps.

• Make sure you have these instructions always open and in front of your eyes.
• Do a backup of all of your files, even if they could be damaged. You should back up your data with a cloud backup solution and insure your files against any type of loss, even from the most severe threats.
• Be patient as this could take a while.

• Scan for Malware
• Fix Registries
• Remove Virus Files

Step 1: Scan for Trojan:Win32/Leonem!rfn with SpyHunter Anti-Malware Tool

1. Click on the "Download" button to proceed to SpyHunter's download page.

Download

Malware Removal Tool

---

It is recommended to run a scan before purchasing the full version of the software to make sure that the current version of the malware can be detected by SpyHunter. Click on the corresponding links to check SpyHunter's EULA, Privacy Policy and Threat Assessment Criteria.

---

2. After you have installed SpyHunter, wait for it to update automatically.

---

3. After the update process has finished, click on the 'Malware/PC Scan' tab. A new window will appear. Click on 'Start Scan'.

---

4. After SpyHunter has finished scanning your PC for any files of the associated threat and found them, you can try to get them removed automatically and permanently by clicking on the 'Next' button.

If any threats have been removed, it is highly recommended to restart your PC.

Step 2: Clean any registries, created by Trojan:Win32/Leonem!rfn on your computer.

The usually targeted registries of Windows machines are the following:

• HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
• HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
• HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunOnce
• HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce

You can access them by opening the Windows registry editor and deleting any values, created by Trojan:Win32/Leonem!rfn there. This can happen by following the steps underneath:

---

1. Open the Run Window again, type "regedit" and click OK.

---

2. When you open it, you can freely navigate to the Run and RunOnce keys, whose locations are shown above.

---

3. You can remove the value of the virus by right-clicking on it and removing it. Tip: To find a virus-created value, you can right-click on it and click "Modify" to see which file it is set to run. If this is the virus file location, remove the value.

Step 3: Find virus files created by Trojan:Win32/Leonem!rfn on your PC.

1.For Windows 8, 8.1 and 10.

For Newer Windows Operating Systems

1: On your keyboard press  + R and write explorer.exe in the Run text box and then click on the Ok button.

2: Click on your PC from the quick access bar. This is usually an icon with a monitor and its name is either “My Computer”, “My PC” or “This PC” or whatever you have named it.

3: Navigate to the search box in the top-right of your PC's screen and type “fileextension:” and after which type the file extension. If you are looking for malicious executables, an example may be "fileextension:exe". After doing that, leave a space and type the file name you believe the malware has created. Here is how it may appear if your file has been found:

N.B. We recommend to wait for the green loading bar in the navigation box to fill up in case the PC is looking for the file and hasn't found it yet.

2.For Windows XP, Vista, and 7.

For Older Windows Operating Systems

In older Windows OS's the conventional approach should be the effective one:

1: Click on the Start Menu icon (usually on your bottom-left) and then choose the Search preference.

2: After the search window appears, choose More Advanced Options from the search assistant box. Another way is by clicking on All Files and Folders.

3: After that type the name of the file you are looking for and click on the Search button. This might take some time after which results will appear. If you have found the malicious file, you may copy or open its location by right-clicking on it.

Now you should be able to discover any file on Windows as long as it is on your hard drive and is not concealed via special software.

Trojan:Win32/Leonem!rfn FAQ

What Does Trojan:Win32/Leonem!rfn Trojan Do?

The Trojan:Win32/Leonem!rfn Trojan is a malicious computer program designed to disrupt, damage, or gain unauthorized access to a computer system. It can be used to steal sensitive data, gain control over a system, or launch other malicious activities.

Can Trojans Steal Passwords?

Yes, Trojans, like Trojan:Win32/Leonem!rfn, can steal passwords. These malicious programs are designed to gain access to a user's computer, spy on victims and steal sensitive information such as banking details and passwords.

Can Trojan:Win32/Leonem!rfn Trojan Hide Itself?

Yes, it can. A Trojan can use various techniques to mask itself, including rootkits, encryption, and obfuscation, to hide from security scanners and evade detection.

Can a Trojan be Removed by Factory Reset?

Yes, a Trojan can be removed by factory resetting your device. This is because it will restore the device to its original state, eliminating any malicious software that may have been installed. Bear in mind that there are more sophisticated Trojans that leave backdoors and reinfect even after a factory reset.

Can Trojan:Win32/Leonem!rfn Trojan Infect WiFi?

Yes, it is possible for a Trojan to infect WiFi networks. When a user connects to the infected network, the Trojan can spread to other connected devices and can access sensitive information on the network.

Can Trojans Be Deleted?

Yes, Trojans can be deleted. This is typically done by running a powerful anti-virus or anti-malware program that is designed to detect and remove malicious files. In some cases, manual deletion of the Trojan may also be necessary.

Can Trojans Steal Files?

Yes, Trojans can steal files if they are installed on a computer. This is done by allowing the malware author or user to gain access to the computer and then steal the files stored on it.

Which Anti-Malware Can Remove Trojans?

Anti-malware programs such as SpyHunter are capable of scanning for and removing Trojans from your computer. It is important to keep your anti-malware up to date and regularly scan your system for any malicious software.

Can Trojans Infect USB?

Yes, Trojans can infect USB devices. USB Trojans typically spread through malicious files downloaded from the internet or shared via email, allowing the hacker to gain access to a user's confidential data.

About the Trojan:Win32/Leonem!rfn Research

The content we publish on SensorsTechForum.com, this Trojan:Win32/Leonem!rfn how-to removal guide included, is the outcome of extensive research, hard work and our team’s devotion to help you remove the specific trojan problem.

How did we conduct the research on Trojan:Win32/Leonem!rfn?

Please note that our research is based on an independent investigation. We are in contact with independent security researchers, thanks to which we receive daily updates on the latest malware definitions, including the various types of trojans (backdoor, downloader, infostealer, ransom, etc.)

Furthermore, the research behind the Trojan:Win32/Leonem!rfn threat is backed with VirusTotal.

To better understand the threat posed by trojans, please refer to the following articles which provide knowledgeable details.