How to get rid of Penumbra stealer

What kind of malware is Penumbra Stealer?

Penumbra Stealer is an information stealer that silently harvests credentials, session data, and sensitive files from infected Windows computers. It targets saved passwords, browser cookies, messaging platform tokens, gaming accounts, and system-level authentication data.

The stealer supports 13 Chromium and Gecko-based browsers and includes a technique to bypass Chrome's App-Bound Encryption, allowing it to extract saved passwords even on fully updated versions of Chrome and similar browsers.

Penumbra Stealer overview

Penumbra Stealer targets 13 Chromium and Gecko-based browsers, extracting saved passwords, cookies, account restore tokens, stored credit card details, autofill entries, physical addresses, browsing history, and bookmarks. It also reads web storage data such as LocalStorage, SessionStorage, and IndexedDB.

For Firefox and other Gecko-based browsers, the stealer natively parses NSS key3/key4 databases to access the browser's internal credential store. On Chromium-based browsers, it uses a combination of LSASS-DPAPI double decryption and CNG/KSP key handling to extract passwords protected by Chrome's App-Bound Encryption.

Messaging and gaming platform targeting

Beyond browsers, Penumbra Stealer collects data from Discord, capturing authentication tokens, MFA status, email address, phone number, billing methods, gift codes, and Nitro subscription status. It also grabs active Telegram session files and identity profiles and session dumps from Tox.

For gaming platforms, the stealer targets Steam by extracting session configuration files and login credentials. It also collects active session files from Minecraft and authentication cookies from Roblox, and performs a complete enumeration of all games installed on the system.

Credentials, system memory, and reconnaissance

Penumbra Stealer collects SSH keys from the user's home directory and automatically detects and packages cryptocurrency wallet files in standard formats.

One of its more serious capabilities is performing a full memory dump of the LSASS process. This captures active security tokens that Windows stores in memory while users are logged in, potentially allowing attackers to access other accounts and services without knowing the actual passwords.

The stealer also harvests stored credentials from Windows Credential Vaults, third-party password managers, TOTP authenticator secrets, FTP client logins, developer credentials, and Outlook profile data.

System reconnaissance

Penumbra Stealer gathers a hardware fingerprint including the system UUID, disk serial numbers, and details about the CPU, GPU, and total RAM. It also records active running processes, connected USB devices, and the network topology of the infected machine.

For location and network profiling, it captures the external IP address and estimates the user's country, region, timezone, and whether a proxy or VPN is in use. On-demand capabilities include taking webcam snapshots and capturing multi-monitor display screenshots.

Conclusion

Penumbra Stealer is a broad-scope threat capable of exposing nearly every account on an infected device. Its combination of browser credential extraction, messaging token theft, gaming session capture, cryptocurrency wallet harvesting, and Windows authentication memory dumps gives attackers extensive material for account takeover, identity theft, and financial loss.

Victims facing such an infection should remove the malware immediately and change passwords for every account and service accessed from the affected device, as tokens and saved credentials may have already been exfiltrated. More examples of stealers are Nyxar, Lunex, and REVSTEALER.

How did Penumbra Stealer infiltrate my computer?

No specific distribution campaign has been publicly attributed to Penumbra Stealer at this time. Like most information stealers, it is likely spread through a combination of methods commonly used to deliver threats of this kind.

Common delivery vectors include phishing emails with malicious attachments, fake software download websites, and pirated content. Software cracks and key generators distributed through file-sharing networks are another frequent source.

Attackers distributing stealers sometimes use YouTube videos promoting a fake utility, cracked application, or trading tool, with a download link in the video description. Any unofficial or untrusted download source is a potential delivery point for threats of this kind.

How to avoid installation of malware?

Do not open attachments or click links in unexpected emails, especially from unknown senders. Download software only from official developer websites or verified app stores, and avoid pirated software, key generators, and unofficial activators, as these are among the most common ways stealers reach victims.

Keep your operating system and all installed applications up to date, and use a reputable security tool with real-time protection. Avoid clicking suspicious advertisements or granting browser notification permissions to unknown sites. If you believe that your computer is already infected, we recommend running a scan with Combo Cleaner Antivirus for Windows to automatically eliminate infiltrated malware.

Penumbra Stealer feature listing:

How to remove malware manually?

Most trojan infections can be removed by running a full system scan with Combo Cleaner. The full manual procedure below is for cases where automatic removal failed, where you want to verify a scan caught everything, or where the threat has multiple persistence points.

Tools you'll need

Combo Cleaner Antivirus 7-days free trial

Recommended primary scanner. VB100 certified. The 7-day free trial is available.

Microsoft Defender Offline Free · built-in

Built into Windows. Boots to a clean environment to catch rootkits.

Process Explorer Free

From Microsoft Sysinternals. Better than Task Manager - shows full paths and signatures.

Autoruns Free

From Microsoft Sysinternals. Lists every place malware can persist on your system.

Microsoft Safety Scanner (MSERT) Free

Official Microsoft on-demand scanner. Always-current signatures - expires every 10 days.

Phase 1~ 5 min

Contain - limit the damage

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1

Disconnect from the network

30 secNo tool needed

Unplug your Ethernet cable and turn off Wi-Fi. If you're on a laptop, the airplane-mode key works fastest.

Why this matters

Many trojans exfiltrate data - saved browser passwords, banking sessions, screenshots - and accept remote commands. Cutting the network stops both immediately. Keep it disconnected until Phase 4.

2

Boot into Safe Mode with Networking

3 min

Safe Mode loads a minimal set of drivers and stops most malware from auto-running. "With Networking" lets you download tools - re-enable Wi-Fi only after you've booted in.

Windows 11

Open Settings → System → Recovery. Click Restart now next to Advanced startup.

Your computer will restart into the "Choose an option" menu. Click Troubleshoot → Advanced options → Startup Settings → Restart. After the second reboot, press 5 or F5.

Windows 10

Click the Windows logo, hold Shift, click the Power icon and choose Restart. In the Choose an option screen, click Troubleshoot → Advanced options → Startup Settings → Restart. Press F5.

Windows 8

Go to the Start Screen, type Advanced, select Settings → Advanced startup options → Restart now → Troubleshoot → Advanced options → Startup settings → Restart → F5.

Note: Windows 8 reached end-of-life in January 2023 - running on it puts you at much higher risk of reinfection.

Windows 7

Click Start → Shut Down → Restart → OK. As the system boots, press F8 repeatedly until the Windows Advanced Options menu appears, then choose Safe Mode with Networking.

Note: Windows 7 reached end-of-life in January 2020 - running on it puts you at much higher risk of reinfection.

Phase 2~ 15 min

Identify - find what's hiding

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3

Inspect running processes with Process Explorer

Tool: Process Explorer5 min

Download Process Explorer from Microsoft Sysinternals. Run it as Administrator. Click Options → Verify Image Signatures and View → Lower Pane View → DLLs.

Sort by "Verified Signer." Anything unsigned running from %AppData%, %LocalAppData%, %Temp%, or %ProgramData% is suspicious. Right-click → Properties to see the full image path. Right-click → "Search Online" to look up unfamiliar process names.

Why not just Task Manager

Task Manager hides full file paths, doesn't show digital signatures, and groups processes in ways that make malware easy to miss. Process Explorer is the same tool Microsoft engineers use.

4

Map every persistence point with Autoruns

Tool: Autoruns 14.x10 min

Download Autoruns. Right-click Autoruns.exe and choose Run as administrator - without elevation, Autoruns can't inspect protected registry hives.

In the menu, open Options → Hide Microsoft Entries and Options → Hide Empty Locations, then click Refresh.

Modern trojans don't just live in startup. Walk through these tabs and look for unsigned or unfamiliar entries:

• Logon - classic Run/RunOnce keys
• Scheduled Tasks - frequent hiding spot, especially tasks with PowerShell, MSHTA, or rundll32 actions
• Services - unsigned services in non-Microsoft folders
• WMI - Event Subscriptions are a stealthy persistence mechanism (MITRE T1546.003)
• Image Hijacks - Image File Execution Options "Debugger" abuse
• AppInit - DLLs loaded into every GUI process
• Browser plug-ins - unsigned add-ons across all installed browsers

Pro tip

Right-click any suspicious entry → "Jump to Image" to see the actual file. Right-click → "Search Online" opens VirusTotal for the file hash. Don't delete yet - just write down the file paths and entry names. We'll remove them after the scans.

5

Check the hosts file and DNS settings

3 minBuilt into Windows

Trojans often redirect bank, antivirus, and update domains to attacker-controlled servers by editing the hosts file or DNS settings.

Hosts file: Open Notepad as Administrator and open C:\Windows\System32\drivers\etc\hosts. Legitimate entries are commented with #. Any uncommented IP-to-domain mapping is suspicious - especially redirects for microsoft.com, windowsupdate, or your bank.

DNS settings: Open Command Prompt as Administrator and run ipconfig /all. Confirm your DNS servers point to your ISP, your router, or a known public resolver (Cloudflare 1.1.1.1, Google 8.8.8.8). Then open Settings → Network & internet → [your adapter] → DNS server assignment and verify both DNS and DNS over HTTPS (DoH) settings haven't been hijacked.

Why this matters

A clean PC with hijacked DNS is still a compromised PC. You'll think you're at chase.com and you'll be at the attacker's clone.

Phase 3~ 60-90 min

Remove - three scans, one cleanup

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No single antivirus catches everything. The order below is intentional: offline scan first (catches rootkits before Windows fully loads), then on-demand scanners on the running system, then manual cleanup of anything they missed.

6

Run Microsoft Defender Offline

Tool: Built into Windows15 min

Reboot to normal Windows. Open Windows Security → Virus & threat protection → Scan options. Select Microsoft Defender Antivirus (offline scan) and click Scan now. Your computer will restart into a stripped-down environment and scan before the full operating system loads.

Why this comes first

Rootkits and bootkits hide from any scanner running on the same Windows session that's already infected. A pre-boot offline scan sees the disk before the malware can hide itself.

Recommended antivirus

Combo Cleaner

VB100 certified. Includes anti-trojan, registry/persistence scanning, anti-spyware in one pass. The 7-day free trial is available.

Download Combo Cleaner

7

Run Combo Cleaner full system scan

Tool: Combo Cleaner20-40 min

Install Combo Cleaner and run a full system scan (not the quick scan). Let it complete fully, review the detected threats, and apply the recommended actions. Combo Cleaner will quarantine known trojans and registry persistence.

8

Run Microsoft Safety Scanner as a second-opinion scan

Tool: Microsoft Safety Scanner15 min

Download Microsoft Safety Scanner (MSERT.exe), Microsoft's free on-demand tool. The binary expires every 10 days, which means every download has the latest signatures. Run a full scan after Combo Cleaner to catch anything one engine alone might miss.

Why a second scan

Different scanning engines catch different threats. Running an additional Microsoft scan after Combo Cleaner is the single most underused verification step in malware removal.

9

Manually remove anything still listed in Autoruns

Tool: Autoruns10 min

Reopen Autoruns. Anything you flagged in Step 4 that's still present hasn't been caught by the automated scans. For each remaining suspicious entry: right-click → Delete in Autoruns (this removes the persistence registration), then navigate to the file path and delete the actual file. Empty the Recycle Bin.

Important

Some malware files reappear after deletion because something else on the system recreates them. If you delete a file and it returns within minutes, you have a remaining persistence point that Autoruns didn't show - usually a service or scheduled task running under SYSTEM. Re-run the scans from Steps 6-8 or proceed to a clean install (see end of guide).

Phase 4~ 15 min

Recover - restore browsers and security

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10

Reset browsers and clear notification permissions

5 min

Trojans and adware frequently hijack browsers - change the default search engine, install rogue extensions, or grant themselves notification permissions to keep displaying scam pop-ups even after the malware is gone.

• Chrome: visit chrome://settings/reset and click "Restore settings to their original defaults." Then visit chrome://settings/content/notifications and remove any unfamiliar sites.
• Edge: visit edge://settings/reset. Then check edge://settings/content/notifications.
• Firefox: open about:support and click Refresh Firefox (Firefox uses "Refresh," not "Reset"). Then check Settings → Privacy & Security → Permissions → Notifications.

Review installed extensions in each browser and remove anything you don't recognize, especially extensions you didn't install yourself.

11

Re-enable Defender, Tamper Protection, and update everything

10 min

Many trojans disable security software. Open Windows Security → Virus & threat protection → Manage settings and confirm Real-time protection, Cloud-delivered protection, and Tamper Protection are all turned on. Tamper Protection prevents malware from disabling Defender silently.

Then run Windows Update (Settings → Windows Update → Check for updates) and update your browsers and applications. The infection vector that let the trojan in originally usually involves outdated software.

Phase 5~ 15 min + 7 days

Verify & secure

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12

Change passwords from a clean device

20 min⚠ Critical

If the trojan was an info-stealer (Lumma, RedLine, Vidar, and similar are extremely common), assume every password saved in your browser is compromised. Change them from a different, known-clean device - your phone is fine if it's not infected.

Recommended order:

1. Primary email first - it's the recovery hub for everything else
2. Banking and financial accounts
3. Password manager master password (if you use one)
4. Social media, shopping, and remaining accounts

Where available, enable phishing-resistant multi-factor authentication (passkeys / FIDO2 hardware keys / authenticator apps) - SMS-based MFA is bypassable by sophisticated attackers.

13

Verify the clean and monitor for 7 days

5 min + 1 week monitoring

Reconnect to the network and run one final full scan with Combo Cleaner. Open Task Manager (Ctrl + Shift + Esc) and switch to the Startup apps tab - confirm nothing suspicious has reappeared.

Over the next 7 days, watch for symptom recurrence: unexpected high CPU usage, unknown processes returning, browser redirects, or pop-ups. If anything returns, you missed a persistence point and the procedure needs to be repeated - or you may have a deeper compromise that requires a clean install.

When to clean install Windows instead

Manual removal isn't always the right answer. Reinstalling Windows from scratch is the only way to be 100% certain when:

• The malware reappears after every removal attempt
• A bootkit or UEFI rootkit was detected (this class of threat sits below the operating system and survives a normal Windows reinstall)
• A confirmed credential-theft trojan ran with administrator privileges (Lumma, RedLine, Vidar) - the system likely has multiple unknown payloads
• The PC is used for online banking, business email, or anything where partial doubt isn't acceptable

A clean install is a 30-60 minute process: Windows 11 reinstall via Settings → System → Recovery → Reset this PC → Remove everything → Cloud download. Back up documents to external storage first, scan the backup with Combo Cleaner before restoring it, and reinstall applications fresh - never restore them from a backup of the infected system.

Important: Manual removal requires advanced computer skills. If you're not confident identifying system files from malicious files, run an automated scan with Combo Cleaner and Windows Defender and stop there - that path catches the vast majority of consumer trojans without the risk of breaking Windows by deleting the wrong file.

Frequently Asked Questions (FAQ)

My computer is infected with Penumbra Stealer malware, should I format my storage device to get rid of it?

Formatting your storage device will remove Penumbra Stealer but will also erase all your files. Running a reputable security tool such as Combo Cleaner is the safer first step and should be tried before reformatting.

What are the biggest issues that Penumbra Stealer malware can cause?

The biggest risks include theft of saved passwords, browser session cookies, cryptocurrency funds, and Windows authentication tokens. These can lead to account takeover, identity theft, unauthorized access to developer or work accounts, and financial loss.

What is the purpose of Penumbra Stealer malware?

Penumbra Stealer is designed to extract as many credentials and sensitive data items as possible from an infected device and send them to the attacker. It targets browser passwords, messaging tokens, gaming credentials, SSH keys, cryptocurrency wallets, and Windows authentication memory.

How did Penumbra Stealer malware infiltrate my computer?

Penumbra Stealer likely reaches victims through phishing emails, fake software download sites, pirated applications, software cracks, or other unofficial download channels. Any untrusted source of software is a potential delivery point for threats of this kind.

Will Combo Cleaner protect me from malware?

Yes. Combo Cleaner can detect and remove most known malware, including information stealers. A full system scan is recommended to ensure all components of an infection are identified and removed.