FileCoder.JER is a file-encrypting ransomware variant that locks your documents, photos, and other personal files, then demands payment (typically in cryptocurrency) to restore access. Like most modern ransomware families, it uses strong cryptographic algorithms that make file recovery without the decryption key effectively impossible through technical means alone. This particular variant has been observed in targeted attacks against both individual users and small businesses, often arriving through malicious email attachments or compromised software downloads.
Once FileCoder.JER executes on a system, it moves quickly to encrypt files across local drives and any connected network shares it can access. Victims typically discover the infection only after their files have been encrypted and renamed with a new extension, at which point a ransom note appears demanding payment within a limited timeframe. The operators behind this ransomware typically demand several hundred to several thousand dollars, with threats to delete the decryption key if payment isn't received promptly.
Threat Profile
| Attribute | Details |
|---|---|
| Malware Family | FileCoder (file-encrypting ransomware) |
| Variant Designation | JER (based on ransom note characteristics or encryption markers) |
| Threat Type | Crypto-ransomware |
| Platform | Windows (all versions vulnerable; typically targets Windows 7–11) |
| Encryption Algorithm | Typical for this family: AES-256 or RSA-2048 hybrid encryption |
| File Extension Added | Varies by campaign (commonly appends random extension or leaves original with marker) |
| Ransom Note Filename | Varies (commonly: DECRYPT_FILES.txt, HOW_TO_DECRYPT.html, or README.txt) |
| Distribution Methods | Phishing emails with malicious attachments, exploit kits, trojanized software installers, RDP brute-force |
| Persistence Mechanism | Often executes from %TEMP% or %APPDATA%, may create Run registry keys or scheduled tasks for ransom note display |
| Network Behavior | May contact C&C servers for key exchange; scans for network shares; typical for this family |
| Data Exfiltration | Some variants collect system information; double-extortion variants upload files before encryption |
| Removal Difficulty | Moderate (removing the malware is straightforward; recovering encrypted files without backups is the challenge) |
How It Spreads
FileCoder.JER primarily arrives through social engineering tactics that trick users into executing the ransomware payload themselves. The most common vector is phishing emails crafted to look like legitimate business correspondence—invoices, shipping notifications, payment confirmations, or HR documents. These emails contain either malicious Office documents with macro scripts or direct executable attachments disguised as PDFs or other document types. When the victim opens the attachment and enables macros (or runs the executable), the ransomware payload downloads and executes.
Beyond email, this ransomware family has been distributed through compromised or trojanized software downloads. Users searching for free versions of commercial software, game cracks, or pirated media files may encounter installers bundled with the ransomware. Exploit kits hosted on compromised websites can also deliver the payload automatically when visitors with outdated browser plugins or operating systems visit infected pages. In some cases targeting businesses, attackers gain access through weak or default Remote Desktop Protocol (RDP) credentials, then manually deploy the ransomware after establishing a foothold.
- Malicious email attachments — weaponized Office documents, JavaScript files in ZIP archives, or direct executables
- Fake software downloads — bundled with pirated applications, key generators, or "free" versions of paid software
- Drive-by downloads — exploit kits targeting browser or plugin vulnerabilities on compromised websites
- RDP brute-force attacks — particularly against small businesses with internet-facing Remote Desktop access
- Malvertising campaigns — malicious advertisements on legitimate websites that redirect to exploit kit landing pages
- Trojanized updates — fake software update notifications that deliver ransomware instead of legitimate patches
What It Does On Your Machine
Upon execution, FileCoder.JER typically copies itself to a location in your user profile directories where it's less likely to be noticed during casual inspection. From there, it begins the encryption process, systematically scanning your drives for target file types—documents, spreadsheets, databases, images, videos, archives, and other personal files. The ransomware deliberately avoids encrypting system files necessary for Windows to function, ensuring the victim can still boot their computer and read the ransom demand.
The encryption process itself uses strong cryptography that generates a unique key for each infected system. This key is encrypted with the attacker's public key and sent to a command-and-control server (or embedded in the ransom note), making decryption without paying the ransom technically impractical in most cases. As files are encrypted, FileCoder.JER typically modifies their extensions, though the specific extension varies by campaign. Some variants append random characters, while others use identifiable markers related to the campaign or victim ID.
Once encryption completes, the ransomware drops ransom notes in multiple locations—typically in every folder containing encrypted files, on the desktop, and sometimes as the desktop wallpaper itself. These notes contain instructions for payment, usually demanding Bitcoin or another cryptocurrency sent to a specific wallet address. The notes often include threats about time limits, increasing ransom amounts, or permanent key deletion if the victim seeks help from authorities or attempts file recovery. In reality, paying doesn't guarantee decryption—some victims report receiving non-functional decryptors or no response after payment.
Manual Removal — Step by Step
Isolate the Infected System Immediately
Disconnect from all networks—unplug the Ethernet cable and disable Wi-Fi. If you're on a business network, also disconnect any external drives or USB storage. This prevents the ransomware from encrypting files on network shares or spreading to other systems. If encryption is actively in progress (you see files changing rapidly), power off the machine immediately to potentially save unencrypted files.
Boot Into Safe Mode with Networking
Restart your computer and repeatedly press F8 (or Shift+F8 on newer systems) during boot to access the Advanced Boot Options menu. Select "Safe Mode with Networking." This loads Windows with minimal drivers and services, preventing most malware from executing automatically while still allowing you to download removal tools if needed.
Identify and Terminate the Ransomware Process
Open Task Manager (Ctrl+Shift+Esc) and look for suspicious processes—random-named executables running from Temp or AppData folders, unfamiliar processes with high CPU usage, or anything named similar to system processes but running from odd locations (like "svchost.exe" from AppData instead of System32). Right-click and select "End Task" on any identified threats. Note the process location before terminating for reference in removal steps.
Remove Persistence Mechanisms
Press Win+R, type "msconfig," and check the Startup tab (or use Task Manager's Startup tab on Windows 8+) for unfamiliar entries. Disable anything suspicious. Then press Win+R again, type "regedit," and navigate to HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run and the equivalent HKEY_LOCAL_MACHINE location. Look for entries pointing to random executables in AppData or Temp folders and delete them. Also check Task Scheduler (taskschd.msc) for unfamiliar scheduled tasks.
Delete the Malware Files
Navigate to the locations you identified in Task Manager—typically %TEMP%, %APPDATA%, or %LOCALAPPDATA% folders. Delete the main executable and any associated folders with GUID-like names. Also delete all ransom note files from your desktop and other folders. If Windows prevents deletion because the file is in use, you may need to boot to Safe Mode without networking or use a bootable antivirus rescue disk.
Run a Comprehensive Malware Scan
Download and run Malwarebytes (free version is sufficient) to scan for any remaining components, registry entries, or associated threats. Follow this with a scan using your existing antivirus software if you have one, or download Microsoft Defender Offline and create a bootable USB to perform a deep scan outside of Windows. Ransomware often arrives with other malware that may have created backdoors or stolen credentials before the encryption occurred.
Check for Shadow Copies (Slim Hope)
Some ransomware variants delete Volume Shadow Copies, but it's worth checking. Open Command Prompt as administrator and type "vssadmin list shadows" to see if any restore points survived. If they exist, you can use System Restore or third-party tools like ShadowExplorer to potentially recover some file versions. Most modern ransomware deletes these automatically, but occasional oversight happens.
Assess File Recovery Options
If you have recent backups on external drives that weren't connected during the infection, those files remain safe. For encrypted files without backups, check nomoreransom.org for free decryption tools—law enforcement and security companies occasionally crack ransomware encryption or recover keys from seized servers. Be realistic though: strong encryption usually means files are unrecoverable without paying, which we never recommend without exhausting all other options first.
Change All Important Passwords
From a confirmed clean device, change passwords for email accounts, banking, cloud storage, and any other sensitive services. Ransomware infections sometimes include information-stealing components that harvest stored credentials. Enable two-factor authentication wherever possible to protect accounts even if passwords were compromised.
Reboot Normally and Verify
Restart your computer normally (not in Safe Mode) and monitor behavior for a day or two. Watch for unusual CPU usage, unexpected network activity, or files appearing in Temp folders. Run another quick scan with Malwarebytes after 24 hours to catch anything that may have attempted to reinstall. If the system behaves normally, the ransomware itself is removed—though encrypted files remain a separate recovery challenge.
Prevention
- Maintain offline backups — Follow the 3-2-1 rule: three copies of important data, on two different media types, with one stored offline or offsite. Ransomware can't encrypt what it can't reach. External drives should be disconnected after backups complete, and cloud backup services should have versioning enabled so you can recover pre-encryption file versions.
- Keep Windows and software updated — Enable automatic Windows updates and keep all software current, especially browsers, PDF readers, Java, and Flash (or better yet, uninstall Flash entirely). Many ransomware infections exploit known vulnerabilities that were patched months or years earlier.
- Use reputable security software — Install and maintain legitimate antivirus/anti-malware software with real-time protection. Windows Defender is adequate for most users if kept current. Supplement with Malwarebytes Premium for behavior-based detection that catches new ransomware variants before signature updates arrive.
- Disable macros by default — Configure Microsoft Office to disable macros in documents from the internet. Most users never need macro functionality, but it's the primary delivery mechanism for ransomware via email attachments. If a document prompts you to "enable content" or "enable macros," treat it with extreme suspicion.
- Practice email caution — Never open attachments from unexpected sources, even if they appear to come from known contacts (email addresses are easily spoofed). Verify unexpected invoices, shipping notifications, or urgent requests by contacting the supposed sender through a different communication channel before opening any attachments.
- Restrict user permissions — Don't use an administrator account for daily computing. Standard user accounts limit ransomware's ability to modify system files or install persistence mechanisms. For home users, create a standard account for everyday use and only elevate privileges when installing legitimate software.
- Secure Remote Desktop access — If you must expose RDP to the internet, use a VPN instead of direct access, implement strong unique passwords, enable Network Level Authentication, and consider changing the default port 3389. Better yet, use zero-trust remote access solutions that don't expose services directly to the internet.
- Show file extensions — Configure Windows to display file extensions for known file types (File Explorer → View → Options → uncheck "Hide extensions for known file types"). This helps identify executable files disguised as documents, like "invoice.pdf.exe" which will appear as "invoice.pdf" with extensions hidden.
Bring It In
Ransomware removal and file recovery assessment require experience and specialized tools that most home users simply don't have. While the malware itself can often be removed following the steps above, determining whether any file recovery options exist—checking for undamaged shadow copies, identifying the specific variant to search for decryptors, analyzing backup remnants, or even negotiating with attackers if absolutely necessary—benefits enormously from professional expertise. More importantly, we can help you understand what happened, how to prevent recurrence, and implement a backup strategy that ensures you're never in this position again.
We're located at 1394 Canton Road in Roswell, just past the QT at Woodstock Road, open Monday through Friday 9 AM to 6 PM and Saturday 10 AM to 4 PM. Bring your infected computer in—no appointment necessary for diagnostics. We'll assess the infection, explain your recovery options honestly (including when paying the ransom might be the only path forward, though we exhaust all other options first), and provide a clear quote before proceeding with any work. Call us at (770) 637-1435 if you have questions or want to discuss your situation before coming in. Ransomware is stressful, but you don't have to deal with it alone.