Trojan:MSIL/Stealer.G is an information-stealing trojan written in Microsoft Intermediate Language (MSIL), the bytecode format used by .NET applications. This malware is designed specifically to harvest credentials, financial data, browser cookies, cryptocurrency wallet information, and other sensitive personal data from infected Windows systems. Once deployed, it operates silently in the background while systematically extracting stored credentials from browsers, email clients, FTP programs, and other applications that cache login information.
The "Stealer.G" designation indicates this is part of a family of similar credential-theft trojans, with the ".G" suffix representing a specific variant or generation within that family. These trojans are typically distributed through malicious email attachments, fake software updates, pirated application cracks, or bundled with seemingly legitimate downloads. The MSIL architecture makes it particularly portable across Windows systems and moderately easy for malware authors to modify and recompile, resulting in numerous variants that share the same core functionality but may evade signature-based detection.
Threat Profile
| Attribute | Details |
|---|---|
| Threat Type | Information-stealing trojan (credential harvester) |
| Family | MSIL-based stealer family, variant G |
| Platform | Windows (all versions with .NET Framework 3.5 or higher) |
| Aliases | MSIL/Stealer.G, Trojan.MSIL.Stealer.G, Win32/Stealer.G (heuristic) |
| Primary Capability | Credential theft from browsers, applications, and system credential stores |
| Persistence Mechanism | Registry Run keys, scheduled tasks, startup folder entries (varies by variant) |
| Distribution Vectors | Email attachments, malicious downloaders, software cracks, trojanized installers |
| Network Behavior | Exfiltrates data via HTTP/HTTPS POST requests to command-and-control servers; may use encryption or encoding |
| Target Data | Browser passwords/cookies, email credentials, FTP clients, crypto wallets, authentication tokens, system information |
| Detection Difficulty | Moderate—well-known signatures exist but variants frequently modified to evade detection |
| Removal Difficulty | Moderate—typically single-component infection but requires thorough credential cleanup afterward |
| Typical File Locations | %APPDATA%\[random folder]\*.exe, %LOCALAPPDATA%\[GUID]\*.exe, %TEMP% directories |
How It Spreads
Trojan:MSIL/Stealer.G reaches victim computers through multiple distribution channels, with malicious email attachments and infected software downloads being the most common vectors. Attackers frequently disguise the trojan as legitimate documents or applications, exploiting users' trust to bypass their natural caution. The MSIL architecture allows the malware to be compiled into deceptively small executables that compress well and transmit quickly, making them ideal for email-based distribution campaigns.
Phishing emails carrying this trojan often impersonate shipping notifications, invoice documents, tax forms, or job applications. The attachment might appear as a PDF or Word document (via executable-disguising filename tricks like "Invoice.pdf.exe") or as a ZIP archive containing the malicious payload. In some campaigns, the initial email attachment is a downloader trojan that fetches and installs the Stealer.G variant after initial infection.
Beyond email, this family of trojans commonly spreads through:
- Pirated software and cracks: Illegitimate download sites bundle the stealer with game cracks, software keygens, or "free" versions of commercial applications
- Fake software updates: Misleading pop-ups claiming your Flash Player, Java, browser, or media codec needs updating—clicking leads to trojan installation
- Malvertising campaigns: Compromised or malicious advertisements on legitimate websites that redirect to exploit kits or direct trojan downloads
- Trojanized utilities: System optimization tools, PC cleaners, or driver update utilities that secretly include credential-stealing components
- Peer-to-peer networks: Torrents and file-sharing platforms where infected files masquerade as movies, software, or document archives
- Watering hole attacks: Compromise of industry-specific websites to target visitors in particular professional sectors
What It Does On Your Machine
Upon execution, Trojan:MSIL/Stealer.G immediately begins reconnaissance to identify what credential-storing applications are present on the infected system. The malware targets browser profile directories where Chrome, Firefox, Edge, Opera, and Brave store login credentials in SQLite database files. It copies these database files—often named "Login Data" or "logins.json"—to a temporary location where it can extract the usernames and encrypted passwords. Modern variants include code to decrypt these credentials by accessing the browser's master key, typically stored in the "Local State" file or Windows Data Protection API (DPAPI) blobs.
Beyond web browsers, the trojan scans for dozens of other applications that cache authentication data. This includes email clients like Outlook, Thunderbird, and Windows Mail; FTP programs such as FileZilla and WinSCP; messaging applications including Discord and Telegram; and cryptocurrency wallet software like Electrum, Exodus, and various browser-based wallet extensions. The malware is particularly aggressive about cryptocurrency-related data, specifically targeting wallet files, recovery phrase documents, and exchange platform credentials stored in password managers or browser autofill databases.
The stolen data is compiled into a structured format—often a text file or ZIP archive—that includes the victim's computer name, Windows username, IP address (as reported by external services), hardware specifications, and a complete inventory of harvested credentials organized by application. This package is then transmitted to the attacker's command-and-control infrastructure via HTTP or HTTPS POST requests. Many variants encrypt or encode this data before transmission to avoid simple network monitoring detection. The entire process from execution to data exfiltration typically completes within 30–90 seconds.
Some variants of Stealer.G establish persistence mechanisms to remain active across system reboots, though many operate as single-execution harvesters that complete their theft and terminate. When persistence is implemented, typical artifacts include:
Manual Removal — Step by Step
Disconnect From All Networks Immediately
Before doing anything else, physically disconnect your computer from the internet by unplugging the ethernet cable or disabling Wi-Fi through the network adapter switch. This prevents the trojan from continuing to transmit stolen credentials and stops attackers from accessing any additional data. Do not skip this step—credential stealers work extremely quickly and may continue exfiltrating data until fully removed.
Boot Into Safe Mode With Networking
Restart your computer and boot into Safe Mode to prevent the trojan from loading automatically. On Windows 10/11, hold Shift while clicking Restart, then navigate to Troubleshoot → Advanced Options → Startup Settings → Restart → press F5 for Safe Mode with Networking. Safe Mode loads only essential Windows components, which typically prevents malware from activating its persistence mechanisms. You'll need networking capability later to download security tools and update passwords.
Identify and Terminate Malicious Processes
Open Task Manager (Ctrl+Shift+Esc) and carefully examine running processes. Look for unfamiliar executables running from unusual locations like %APPDATA%, %LOCALAPPDATA%, or %TEMP% folders with random names or deceptive names like "svchost.exe" not running from System32. MSIL/Stealer trojans often have minimal CPU usage but may show network activity. Right-click suspicious processes, select "Open File Location" to verify the path, then end the process. Note the file location for deletion in the next step.
Remove Persistence Mechanisms
Press Win+R and type "msconfig" to open System Configuration. Navigate to the Startup tab (on Windows 10/11, this opens Task Manager's Startup tab) and disable any unfamiliar startup items pointing to suspicious locations. Next, open Task Scheduler (search for it in Start menu), examine the Task Scheduler Library, and delete any recently created tasks with suspicious names or that execute files from non-standard locations. Finally, check the Startup folder at shell:startup by typing that into the Run dialog and remove any suspicious shortcuts.
Delete the Trojan Executable and Associated Files
Navigate to the file locations you identified in Step 3 and delete the entire containing folder. Common locations include folders with GUID names in %LOCALAPPDATA%, random-named folders in %APPDATA%\Microsoft\Windows\, or temporary directories. You may need to enable viewing of hidden files and folders (File Explorer → View → Options → View tab → Show hidden files). If Windows prevents deletion claiming the file is in use, proceed to Step 6 first, then return to delete these files after running the security scanner.
Run a Comprehensive Antimalware Scan
Download and install Malwarebytes Free from a clean computer, transfer it via USB drive if your infected machine is still offline, or reconnect briefly to download it directly. Run a full "Threat Scan" which examines all drives, registry locations, and common hiding spots. Malwarebytes maintains excellent detection signatures for MSIL-based stealers. Quarantine and remove all detected threats. Additionally, run a second-opinion scan with your existing antivirus software if available, or use Windows Defender's offline scan feature (Windows Security → Virus & threat protection → Scan options → Microsoft Defender Offline scan).
Clean and Reset All Web Browsers
Since the trojan accessed your browser credential stores, you should reset each affected browser to defaults. In Chrome/Edge, go to Settings → Reset settings → Restore settings to their original defaults. In Firefox, go to Help → More Troubleshooting Information → Refresh Firefox. This clears potentially compromised stored data while preserving bookmarks. After resetting, clear all browsing data including cookies, cached data, and site settings from the beginning of time. Do not sign back into browser sync accounts until you've changed those passwords from a known-clean device.
Change All Credentials From a Clean Device
Using a different computer, tablet, or smartphone that was never infected, immediately change passwords for all critical accounts: email, banking, online shopping, social media, work-related services, and cryptocurrency exchanges. Enable two-factor authentication on every service that offers it—this provides critical protection even if attackers obtained your passwords. Start with your primary email account since it controls password reset for other services, then move to financial accounts, then everything else. Assume every credential stored in your browsers was compromised.
Monitor Financial Accounts and Enable Alerts
Contact your bank and credit card companies to inform them of the potential credential theft. Request enhanced monitoring on your accounts and consider placing a fraud alert or temporary freeze on your credit with the three major bureaus (Equifax, Experian, TransUnion). Review recent transactions carefully for any unauthorized activity. If you use cryptocurrency wallets that were installed on the infected machine, transfer funds to newly created wallets with fresh recovery phrases generated on a clean device—never reuse a wallet that existed on the compromised system.
Reboot and Verify System Cleanliness
Restart your computer normally (not in Safe Mode) and verify the trojan has not returned. Monitor Task Manager for several minutes after boot to ensure no suspicious processes launch. Run another quick scan with Malwarebytes and Windows Defender to confirm the system is clean. Test browser functionality and verify your new passwords work correctly. Over the following week, remain vigilant for signs of reinfection such as unusual network activity, unexpected password reset emails, or unfamiliar startup programs appearing.
Prevention
- Never open unexpected email attachments—even if they appear to come from known senders. Verify with the sender through a separate communication channel before opening attachments, especially executable files, ZIP archives, or documents with unusual double extensions like ".pdf.exe"
- Download software only from official sources—avoid third-party download sites, crack/keygen repositories, and torrent platforms for software acquisition. Pirated software is the single most common vector for trojan delivery. If software costs money, either pay for it or find a legitimate free alternative
- Keep Windows and all applications updated—enable automatic updates for Windows, web browsers, Java, Adobe products, and other commonly exploited software. Many stealer infections begin with exploitation of unpatched vulnerabilities in outdated software that then downloads the credential-theft payload
- Use a reputable security suite with real-time protection—Windows Defender provides baseline protection, but consider augmenting it with Malwarebytes Premium or another respected security product that offers behavioral analysis and exploit protection. Keep definitions updated automatically
- Employ a password manager with strong encryption—services like Bitwarden, 1Password, or KeePass store credentials in encrypted vaults that are much more difficult for stealers to compromise than browser-stored passwords. Use unique, complex passwords for every account—if one gets compromised, others remain secure
- Enable two-factor authentication everywhere possible—even if attackers steal your password, 2FA provides a second barrier they must overcome. Use authenticator apps rather than SMS when possible, as SMS-based 2FA can be compromised through SIM-swapping attacks
- Maintain skepticism toward urgent requests and offers—whether received by email, social media, or pop-up advertisement, urgent language ("Your account will be closed!", "Download this update now!") is a hallmark of social engineering. Legitimate companies don't operate this way. Navigate directly to the official website rather than clicking links in suspicious messages
- Regularly back up important data to offline storage—while stealers don't typically destroy data like ransomware does, complete system reimaging is sometimes necessary after severe infections. Weekly backups to an external drive that's disconnected when not in use ensures you can recover if the worst happens without losing irreplaceable files
Bring It In
Credential-stealing trojans like MSIL/Stealer.G represent a serious threat to your financial security, privacy, and digital identity. While the manual removal steps above can eliminate the infection, the aftermath requires careful attention to credential rotation, financial monitoring, and system security hardening that goes beyond simply deleting files. If you're uncertain about any step in the removal process, if scans continue detecting threats, or if you want professional assurance that every trace has been eliminated and your system properly secured, we're here to help.
Computer Repair Roswell has extensive experience with information-stealing trojans and the comprehensive cleanup they require. We'll thoroughly remove the infection, verify complete eradication, help you secure compromised accounts, and configure your system with appropriate defenses to prevent reinfection. Our shop is located at 1000 Holcomb Woods Parkway in Roswell, Georgia—just call us at (770) 679-9004 or stop by during business hours. Same-day service is often available for malware emergencies, and we'll walk you through exactly what was found and what steps we took to protect your digital life going forward. Don't gamble with your financial security—let professionals ensure the job is done right.