Trojan:FileCoder.QE is a file-encrypting ransomware variant that locks victims' documents, photos, databases, and other personal files using strong cryptographic algorithms. Once it gains access to a system, this malware rapidly encrypts files across local drives and connected network shares, appending distinctive file extensions and dropping ransom notes demanding payment for decryption keys. Like other FileCoder family members, it combines trojan delivery methods with aggressive encryption behavior designed to maximize pressure on victims.
While the .QE designation indicates a specific detection signature variant, the underlying ransomware follows patterns typical of modern crypto-malware: silent infiltration, rapid file enumeration, strong encryption, and staged C&C communication for key exchange. Victims typically discover the infection only after their files become inaccessible and ransom demands appear across their desktop and affected folders.
Threat Profile
| Family | FileCoder ransomware family (trojan-based file encryptor) |
| Classification | Trojan:FileCoder, Ransomware, Crypto-malware |
| Aliases | Ransom:Win32/FileCoder, Trojan.Encoder.QE, FileCryptor.QE (varies by AV vendor) |
| Platform | Windows (XP through 11; primarily targets Windows 7–10 systems) |
| Discovery Period | Mid-to-late 2010s (specific .QE signature variant; FileCoder family active since early 2010s) |
| Distribution Methods | Malicious email attachments, exploit kits, RDP brute-force, software cracks, drive-by downloads |
| Encryption Algorithm | Typically AES-256 or RSA hybrid encryption (standard for this family) |
| File Extensions Targeted | Documents (.docx, .pdf, .xlsx), images (.jpg, .png, .psd), databases (.sql, .mdb), archives (.zip, .rar), and 200+ common file types |
| Persistence Mechanism | Registry Run keys, scheduled tasks, modifications to startup folders (varies by variant) |
| Network Behavior | C&C communication for key exchange, potential lateral movement via SMB, may scan for network shares |
| Payload Delivery | Multi-stage: dropper downloads encryptor module, establishes persistence, then executes encryption routine |
| Removal Difficulty | Moderate (payload removal straightforward; file decryption without keys extremely difficult) |
How It Spreads
Trojan:FileCoder.QE reaches victim systems through multiple attack vectors, with malicious email campaigns serving as the primary distribution method. Threat actors craft convincing phishing messages impersonating shipping notifications, invoice requests, tax documents, or urgent business correspondence. These emails contain weaponized attachments—often Office documents with malicious macros, PDF files with embedded exploits, or compressed archives containing executable payloads disguised as legitimate documents.
The trojan component is crucial to its distribution strategy. Unlike worms that spread automatically, FileCoder variants require the victim to execute the initial payload, whether by enabling macros in a document, double-clicking what appears to be an invoice PDF, or running a fake installer. This social engineering component makes user awareness a critical defense layer.
Beyond email, this ransomware family spreads through:
- Compromised Remote Desktop Protocol (RDP) sessions — Attackers scan for exposed RDP ports (3389) and use credential-stuffing or brute-force attacks to gain access, then manually deploy the ransomware
- Exploit kits on compromised websites — Drive-by downloads targeting unpatched browsers or plugins (Flash, Java, Silverlight) that silently install the dropper without user interaction
- Software piracy and crack sites — Fake game cracks, key generators, or pirated software bundles that contain the trojan as a secondary payload
- Malicious advertisements (malvertising) — Compromised ad networks serving poisoned ads that redirect to exploit landing pages or initiate fake download prompts
- Secondary infections from other malware — Existing trojans like Emotet or TrickBot downloading FileCoder as a follow-on payload after establishing initial access
- USB and removable media — Infected systems may spread autorun-enabled versions to connected external drives (less common for targeted ransomware)
What It Does On Your Machine
Once executed, Trojan:FileCoder.QE follows a carefully orchestrated infection sequence designed to maximize file encryption while evading detection. The initial dropper—often a small executable or script—performs environment checks to avoid execution in sandboxed analysis environments. If it determines the system is a legitimate target, it downloads or unpacks the main encryption module, typically placing it in a randomly-named folder within the user's AppData directory.
The malware establishes persistence immediately, ensuring it survives reboots should the encryption process be interrupted. It creates registry entries in the Windows Run key locations and may deploy scheduled tasks configured to trigger at user logon or system startup. Some variants modify Windows Defender exclusion lists to prevent scanning of their operational folders, though this requires elevated privileges not always available.
Before beginning encryption, FileCoder variants typically communicate with command-and-control infrastructure to register the new victim and receive a unique encryption key pair. This key exchange ensures that each victim receives a unique decryption key held exclusively by the attackers. The malware may also attempt to enumerate network shares, mapped drives, and cloud storage synchronization folders (Dropbox, OneDrive, Google Drive) to maximize encryption scope. Many variants deliberately avoid encrypting system files critical to Windows operation—they want the computer functional enough for victims to see ransom notes and make payments.
The encryption process itself is remarkably fast. FileCoder.QE scans directories for target file extensions, encrypts their contents using strong cryptographic algorithms (typically AES-256 for speed with RSA-2048 for key protection), and renames them with a distinctive extension or suffix. Original filenames may be preserved or randomized depending on the variant. After encrypting each directory, the ransomware drops a ransom note—usually a .txt or .html file with names like "HOW_TO_DECRYPT.txt" or "RECOVER_FILES.html"—containing payment instructions, Bitcoin wallet addresses, contact information for "support," and threatening deadlines. These notes are placed in every affected folder, on the desktop, and sometimes set as the desktop wallpaper for maximum visibility.
Manual Removal — Step by Step
Isolate the Infected System Immediately
Disconnect from all networks—unplug the Ethernet cable and disable Wi-Fi through the physical switch or by removing the adapter. If the computer is part of a home or business network, this prevents the ransomware from encrypting files on shared drives or spreading to other machines. If possible, also disconnect external drives, USB sticks, and NAS devices. Power down the machine if you catch the infection during active encryption (desktop wallpaper changing, high disk activity, ransom notes appearing). Document which files still appear accessible—this helps assess encryption progress.
Boot into Safe Mode with Networking
Restart the computer and enter Safe Mode, which loads only essential Windows components and prevents most malware from auto-starting. For Windows 10/11: hold Shift while clicking Restart, then navigate to Troubleshoot → Advanced Options → Startup Settings → Restart, and select option 5 (Safe Mode with Networking). For Windows 7: restart and tap F8 repeatedly before the Windows logo appears, then select Safe Mode with Networking. This environment allows you to work while limiting the malware's ability to interfere, and the networking component lets you download removal tools.
Identify and Terminate Malicious Processes
Open Task Manager (Ctrl+Shift+Esc) and look for suspicious processes—particularly those with random names in the AppData or Temp folders, or legitimate-sounding names like "svchost.exe" running from unusual locations (genuine svchost.exe runs from System32). Right-click suspicious processes, select "Open file location," and note the path. Do NOT click "End task" yet—first check if this process is respawned by a scheduled task or Run key. Use Autoruns (from Microsoft Sysinternals) if available to see what launches at startup. Once identified, end the process and immediately proceed to persistence removal.
Remove Persistence Mechanisms
Open Registry Editor (regedit.exe) and navigate to HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run and HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run. Look for entries pointing to suspicious executables in AppData or Temp folders and delete them. Next, open Task Scheduler (taskschd.msc) and examine the task library for suspicious scheduled tasks—delete any that reference the malware paths. Check the Startup folder at %APPDATA%\Microsoft\Windows\Start Menu\Programs\Startup for malicious shortcuts. Be thorough: persistence is what allows the malware to survive a reboot.
Delete the Malware Files and Folders
Navigate to the folder locations identified in step 3 (typically in %LOCALAPPDATA% or %TEMP%) and delete the entire malware folder. You may need to take ownership of the folder if access is denied (right-click → Properties → Security → Advanced → Change owner to your account). Empty the Recycle Bin immediately afterward. Check both your user profile's Temp folder and the system-wide C:\Windows\Temp directory for dropper remnants. Don't assume deleting one file is sufficient—ransomware often deploys multiple components across different locations.
Run Comprehensive Malware Scans
Download and install a reputable anti-malware tool if you don't already have one—Malwarebytes Free is effective for ransomware removal. Update the definitions, then run a full system scan (not quick scan). Follow up with a second-opinion scanner like HitmanPro or Emsisoft Emergency Kit. These specialized tools often detect components that traditional antivirus misses. Don't skip this step even if you think you've manually removed everything—ransomware frequently installs backdoors or additional trojans that enable reinfection or data theft.
Reset Web Browsers (If Applicable)
Some FileCoder variants modify browser settings or install extensions to monitor activity or prevent access to security sites. Open each browser and reset to default settings: for Chrome, go to Settings → Advanced → Reset and clean up → Restore settings to defaults. For Firefox: Help → More Troubleshooting Information → Refresh Firefox. For Edge: Settings → Reset settings → Restore settings to default values. This removes potentially malicious extensions and clears startup hijacks without losing essential bookmarks (which sync or can be backed up separately).
Assess File Damage and Recovery Options
Once the system is clean, evaluate which files were encrypted. Do NOT attempt to decrypt using tools found through random internet searches—many fake "decryptors" are additional malware. Check if legitimate decryption tools exist for your specific ransomware variant at NoMoreRansom.org (a law enforcement project with free decryptors). If you have recent backups on external drives that weren't connected during the attack, use those. Windows System Restore may recover some files if it wasn't disabled by the malware. Shadow Volume Copies (via ShadowExplorer tool) sometimes survive. For critical data without backups, professional data recovery services may help, but set realistic expectations.
Change All Passwords from a Clean Device
Many ransomware infections include information-stealing components that capture credentials before or during the encryption attack. From a known-clean device (not the infected one, even after cleaning), change passwords for all critical accounts: email, banking, work systems, cloud storage, and social media. Enable two-factor authentication wherever possible. If the infected machine was used for business, notify your IT department immediately—credential compromise could affect entire networks. Monitor financial accounts closely for several months following the infection.
Reboot Normally and Verify System Stability
Restart the computer in normal mode (not Safe Mode) and observe its behavior carefully. Monitor startup time, CPU usage, network activity, and whether any suspicious processes reappear. Run another quick scan with your anti-malware tool. Check that all legitimate applications launch correctly and that no ransom notes reappear. Test a few encrypted files to confirm encryption is no longer progressing. If everything appears stable after 24-48 hours of normal use, the active infection is likely resolved—though file recovery remains a separate challenge requiring backups or specialized tools.
Prevention
- Maintain offline backups using the 3-2-1 rule: Keep three copies of important data on two different media types, with one copy stored offline (external drive disconnected except during backups, or cloud backup with versioning). Ransomware can only encrypt files it can reach—offline backups remain safe.
- Keep Windows and all software current with security patches: Enable automatic updates for the operating system and set applications to update automatically. Many ransomware infections exploit known vulnerabilities that were patched months or years earlier. Pay special attention to Adobe products, Java, and browsers.
- Deploy reputable antivirus with real-time protection: Free solutions from Microsoft (Defender), Malwarebytes, or Kaspersky provide baseline protection. Ensure real-time scanning is enabled and definitions update daily. Consider business-grade solutions with behavioral detection for work machines handling sensitive data.
- Train yourself and employees to recognize phishing attempts: Be skeptical of unexpected email attachments, especially Office documents from unknown senders or invoices you didn't request. Verify sender identity through separate communication channels (phone call, not reply email). Avoid enabling macros in documents unless absolutely necessary and expected.
- Restrict user account privileges: Operate under a standard user account for daily activities rather than an administrator account. Ransomware with administrative privileges can modify system files, disable security software, and encrypt more thoroughly. Use the admin account only when installing legitimate software.
- Disable Remote Desktop Protocol if not required: If you must use RDP for remote access, move it to a non-standard port, require VPN connection first, implement account lockout policies, use strong/unique passwords, and enable Network Level Authentication. RDP is a major enterprise ransomware vector.
- Configure Windows to show file extensions: In File Explorer, enable "File name extensions" under the View tab. This reveals when "invoice.pdf" is actually "invoice.pdf.exe"—a common disguise for malware. Many users inadvertently execute malicious files thinking they're documents.
- Use email filtering and web content filters: Enable spam filtering on email accounts to catch phishing attempts before they reach your inbox. Consider browser extensions or DNS-level filtering (OpenDNS, Cloudflare for Families) to block access to known malware distribution sites and exploit kit landing pages.
When Computer Repair Roswell removes ransomware and cleans your infected system, we stand behind our work with a 90-day warranty. If this specific threat returns within 90 days through no fault of your own (not reinfection from clicking another malicious link), we'll fix it again at no charge. We also provide guidance on backup solutions and security configurations to prevent future infections. Your peace of mind is part of the service.
Bring It In
Ransomware removal and file recovery require specialized expertise, particularly when dealing with encryption variants like Trojan:FileCoder.QE. While the removal steps above can work for technically confident users, most people benefit from professional assistance—especially when critical business documents, family photos, or financial records are at stake. Our team at Computer Repair Roswell has encountered countless ransomware cases and understands both the technical removal process and the emotional toll these infections take. We can assess whether decryption is possible, recover files from shadow copies or backup sources you might not know exist, and—most importantly—prevent reinfection through proper system hardening.
We're located right here in Roswell, Georgia, ready to help whether you're a homeowner with an infected laptop or a small business dealing with encrypted accounting files. Don't let ransomware derail your day or threaten your livelihood. Call us at (770) 667-9487 or stop by our shop during business hours. We'll provide a free diagnostic assessment, explain your options clearly (including realistic expectations about file recovery), and get your system cleaned and protected. Bring your machine in—we'll take it from there and get you back up and running with the data security you need to work and live with confidence.