Trojan:MSIL/SunnyDigits is a detection name for malicious software written in the Microsoft Intermediate Language (MSIL/.NET framework) that typically functions as a credential stealer and system infiltration tool. First observed in mid-2022, this trojan has appeared in multiple variants targeting Windows systems with the primary goal of harvesting sensitive information—passwords, browser credentials, cryptocurrency wallet data, and authentication tokens. Unlike simple adware or browser hijackers, SunnyDigits represents a genuine security threat capable of causing financial loss and identity theft.
The trojan's name derives from its tendency to generate numeric identifiers ("digits") for infected systems while maintaining persistence through scheduled tasks that execute at "sunny" intervals—regular daytime hours when users are typically active and less likely to notice system slowdowns. Security researchers have documented connections between SunnyDigits and broader malware distribution networks that package it alongside fake software updates and pirated application installers.
Threat Profile
| Attribute | Details |
|---|---|
| Threat Family | Information Stealer / Credential Harvester Trojan |
| Aliases | MSIL/SunnyDigits, Trojan.MSIL.SunnyDigits.A, InfoStealer.SunnyDigits, Win32/SunnyDigits (varies by AV vendor) |
| Platform | Windows 7/8/8.1/10/11 (requires .NET Framework 4.0 or higher) |
| First Discovered | June 2022 |
| Primary Distribution | Bundled with pirated software, fake updates, malicious email attachments, drive-by downloads |
| Persistence Mechanism | Registry Run keys, scheduled tasks, startup folder entries |
| Key Capabilities | Credential theft, browser data extraction, screenshot capture, keylogging (in some variants), cryptocurrency wallet targeting |
| Typical File Size | 120-450 KB (MSIL executables, varies by variant and packing) |
| Network Behavior | HTTPS exfiltration to compromised servers, often disguised as legitimate traffic; C2 communication on non-standard ports |
| IoC Indicators | GUIDs in %LOCALAPPDATA%, scheduled tasks with random names, modified browser profile data, outbound HTTPS to suspicious domains |
| Data Targets | Chrome/Firefox/Edge credentials, Discord tokens, Steam sessions, cryptocurrency wallets (Exodus, Electrum, Atomic), FileZilla credentials |
| Removal Difficulty | Moderate—requires safe mode boot, manual registry cleanup, and thorough scanning |
How It Spreads
Trojan:MSIL/SunnyDigits reaches victim computers through social engineering and software bundling tactics rather than exploiting zero-day vulnerabilities. The threat actors behind this malware rely on users unknowingly executing infected files, often disguised as legitimate installers or documents. Distribution campaigns typically spike during major software release cycles when users search for cracks, keygens, or "free" versions of paid applications.
The most common infection vector involves fake software installers downloaded from file-sharing sites, torrent trackers, or YouTube-linked download pages. A user searching for "Adobe Photoshop crack" or "Windows activator" encounters a website offering the desired software—but the download package includes SunnyDigits bundled within the installer. The malware executes silently in the background while the decoy software may actually install, creating the illusion of a successful download.
Email-based distribution occurs through phishing campaigns disguised as shipping notifications, invoice attachments, or security alerts. These emails contain ZIP or RAR archives with executables inside, or malicious Microsoft Office documents with macros that download and execute the trojan when enabled.
- Pirated software bundles — Cracks, keygens, and "portable" versions of commercial software downloaded from torrent sites or file-sharing platforms
- Fake update prompts — Websites displaying fake Adobe Flash, Chrome, or Windows update notifications that deliver malware instead of legitimate updates
- Malicious email attachments — ZIP files containing .exe files disguised with document icons, or Office documents with macro-based downloaders
- Trojanized utilities — Modified versions of popular freeware tools (video converters, PDF readers, system optimizers) re-uploaded to third-party download sites
- Malvertising campaigns — Compromised ad networks serving malicious advertisements that redirect to drive-by download pages
- YouTube scam links — Tutorial videos for software cracks linking to file-hosting services (MediaFire, Mega, etc.) containing infected downloads
What It Does On Your Machine
Once executed, Trojan:MSIL/SunnyDigits immediately begins its reconnaissance and data collection routine. The malware first checks for common virtualization artifacts and debugging tools—an anti-analysis technique to avoid detection in security research environments. If it determines it's running on a genuine user system, it proceeds to establish persistence by creating scheduled tasks and registry entries that ensure it runs automatically after every reboot.
The trojan's primary mission is credential harvesting. It targets browser profile directories where Chrome, Firefox, Edge, and Opera store saved passwords, cookies, and autofill data. The malware specifically searches for login credentials to financial services, email accounts, social media platforms, and cryptocurrency exchanges. Browser session tokens are particularly valuable because they allow attackers to bypass two-factor authentication and access accounts without needing passwords. Discord tokens receive special attention—compromised Discord accounts are frequently used to spread malware to the victim's contact list or to hijack servers for crypto scams.
Beyond browsers, SunnyDigits scans for installed cryptocurrency wallet applications. It creates copies of wallet.dat files and seed phrase backups from applications like Exodus, Electrum, and Atomic Wallet. For FileZilla FTP clients, it extracts stored server credentials from XML configuration files. Some variants include basic keylogging capabilities that record keystrokes when banking sites or cryptocurrency exchange URLs are detected in the browser title bar. The collected data is compressed, encrypted, and transmitted to attacker-controlled servers via HTTPS connections that blend in with normal web traffic.
Throughout this process, the malware attempts to avoid detection by operating during periods of high system activity and limiting CPU usage. It may pause data collection when full-screen applications are running or when the system is idle, resuming only when the user appears actively engaged with the computer. This behavior pattern makes it particularly difficult for users to notice performance degradation or unusual network activity.
Manual Removal — Step by Step
Disconnect from the Network Immediately
Unplug your Ethernet cable or disable Wi-Fi to prevent the trojan from transmitting any additional stolen data. This also prevents the malware from receiving updated instructions from its command-and-control server. Work offline throughout the entire removal process.
Boot Into Safe Mode with Networking
Restart your computer and repeatedly press F8 (or Shift+F8 on Windows 10/11) before Windows loads. Select "Safe Mode with Networking" from the boot options menu. This loads Windows with minimal drivers and prevents most malware from auto-starting, making removal safer and more effective.
Terminate Malicious Processes
Open Task Manager (Ctrl+Shift+Esc) and look for suspicious processes—particularly those named "svchost.exe" running from user directories rather than System32, or processes with random names consuming network bandwidth. Right-click and select "End Task" on any suspicious processes. Note the file location before terminating.
Remove Scheduled Task Persistence
Open Task Scheduler (search for it in the Start menu) and examine the Task Scheduler Library. Look for tasks with generic Microsoft-sounding names that point to executables in AppData\Local folders. Delete any scheduled tasks that reference suspicious GUID-named folders or executables you don't recognize. Common fake names include "MicrosoftEdgeUpdate," "WindowsDefenderUpdate," or "SystemMonitorService."
Clean Registry Run Keys
Press Win+R, type "regedit," and navigate to HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run and the same path under HKEY_LOCAL_MACHINE. Look for entries pointing to executables in AppData\Local\{GUID} folders or with suspicious names. Right-click and delete these entries. Also check the RunOnce keys in the same locations.
Delete the Malware Files
Navigate to the file locations you identified in Task Manager (typically C:\Users\[YourName]\AppData\Local\). Delete any folders with GUID names (like {3F2504E0-4F89-11D3-9A0C-0305E82C3301}) that contain the malicious executable. Also check your Startup folder at C:\Users\[YourName]\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup\ for any suspicious shortcut files.
Run Malwarebytes and a Secondary Scanner
Download Malwarebytes (from malwarebytes.com—verify the URL carefully) and run a full system scan. Follow up with a scan from Microsoft Defender Offline or ESET Online Scanner for a second opinion. These tools often catch remnants and related PUPs that manual removal misses. Quarantine and delete all detected threats.
Reset Browser Settings and Clear Data
Open each installed browser and reset it to default settings—this removes malicious extensions and restores safe defaults. In Chrome: Settings > Reset settings > Restore settings to their original defaults. In Firefox: Help > More Troubleshooting Information > Refresh Firefox. Clear all browsing data, cookies, and cached files from the beginning of time.
Change All Important Passwords
Since SunnyDigits specifically targets stored credentials, assume all saved passwords have been compromised. From a DIFFERENT, clean device (your phone or another computer), change passwords for your email, banking, social media, and any cryptocurrency exchange accounts. Enable two-factor authentication everywhere it's available. If you use a password manager, change its master password as well.
Reboot Normally and Verify Removal
Restart your computer normally (exit Safe Mode) and observe startup behavior. Check Task Manager for suspicious processes, verify your scheduled tasks list is clean, and run one final quick scan with your antivirus. Monitor your system for the next few days—unusual slowdowns, unexpected network activity, or browsers opening on their own may indicate incomplete removal.
Prevention
- Never download software from torrent sites or unofficial sources. Pirated software is the primary distribution method for credential-stealing trojans. Use official vendor websites or verified app stores exclusively. The "free" cracked version costs far more in stolen data than the legitimate license would have.
- Keep Windows Defender and your operating system updated. Microsoft releases definition updates multiple times daily. Enable automatic updates and ensure Windows Defender real-time protection is active. Modern Windows 10/11 systems have excellent built-in protection if kept current.
- Disable macros in Microsoft Office by default. Go to File > Options > Trust Center > Trust Center Settings > Macro Settings and select "Disable all macros with notification." Only enable macros for documents from verified, trusted sources—and even then, verify through a separate communication channel that the sender intended to include macros.
- Use a password manager instead of browser-saved passwords. Quality password managers like Bitwarden, 1Password, or KeePass encrypt credentials with your master password and aren't as easily harvested as browser-stored data. They also make it easier to use unique passwords for every account.
- Enable two-factor authentication on critical accounts. Even if malware steals your password, 2FA prevents immediate account access. Prefer authenticator apps or hardware keys over SMS-based codes. Focus especially on email, banking, and cryptocurrency accounts.
- Be skeptical of unexpected email attachments. Never open attachments from unknown senders. For expected attachments from known contacts, verify through a separate communication method (text message, phone call) that they actually sent the file—compromised accounts frequently send malware to all contacts.
- Maintain regular backups of critical data. Use the 3-2-1 rule: three copies of data, on two different types of media, with one stored off-site. Keep at least one backup completely offline and disconnected. This protects against ransomware variants and system failures equally.
- Monitor your financial accounts and credit reports regularly. Set up alerts for transactions on bank and credit card accounts. Check your credit report quarterly for unfamiliar accounts or inquiries. Early detection of fraud limits damage significantly.
Bring It In
Trojan:MSIL/SunnyDigits represents a serious threat to your personal information and financial security. While the manual removal steps above work for technically confident users, credential-stealing malware often leaves hidden remnants or comes bundled with additional threats that generic scanners miss. A single overlooked registry key or persistence mechanism means reinfection within hours. More importantly, if you've had this infection for any length of time, your passwords, browser sessions, and potentially cryptocurrency wallets have already been compromised—the question isn't whether to clean your computer, but how thoroughly and how quickly.
Computer Repair Roswell specializes in complete malware remediation for North Atlanta residents and businesses. We perform forensic-level cleaning that goes beyond what automated tools catch, manually verify every persistence location, and provide detailed guidance on securing your accounts after credential theft. Our flat-rate virus removal service includes priority same-day appointments, and we'll have you back up and running securely—usually within hours, not days. Located at 1000 Mansell Road in Roswell, we're open Monday through Saturday to serve you. Call (770) 637-1435 or stop by our shop. Bring your infected computer in today, and we'll make sure SunnyDigits and anything it brought along are completely gone—with our 90-day guarantee backing that promise.