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What kind of malware is STX?
STX is a remote access Trojan (RAT) that cybercriminals were observed spreading through fake or trojanized software installers. The RAT steals passwords, browser data, crypto-wallet details, and other sensitive information after connecting to its command-and-control server. It also uses anti-detection and anti-analysis techniques.
More about STX
First, STX checks if it is running inside a virtual machine (VM). It looks for signs of popular VM programs like VirtualBox, VMware, and QEMU and files, registry keys, drivers, or services installed by those programs. If it finds any of them, it closes itself. This helps the RAT avoid detection.
The malware also checks if it is being analyzed by security tools (such as Avast, Trend Micro, Sophos, Symantec, and others). It looks for a debugger and ensures it is running via PowerShell or MSBuild. If not, it exists. Then, STX hides its own window from the Taskbar and Alt+Tab menu. It looks for the Windows Terminal window and changes its settings so it stays hidden.
Once STX has gone through the initial steps, it can carry out various malicious actions. The RAT can update itself by downloading and running new malware from the attackers. It can steal saved credentials, remove itself, and delete persistence files. Also, it can run PowerShell scripts, programs, DLL files, or shellcode directly in memory.
Furthermore, the RAT gives attackers a hidden remote desktop to secretly control the infected device. Cybercriminals can type keys, move the mouse, scroll, and paste text on the hidden desktop. It can also switch between hidden desktops. The malware can also route traffic through the victim's device.
STX can steal saved usernames and passwords from browsers like Brave, Chrome, Edge, and Firefox. It can also collect browser cookies, saved Windows Vault credentials, and login details from FTP programs like FileZilla, WinSCP, and Cyberduck. The malware also looks for desktop cryptocurrency wallets such as Electrum, Bitcoin-Qt, and Litecoin-Qt.
Additionally, the RAT makes itself run even after the infected computer restarts. It uses PowerShell or MSBuild to secretly run its code in memory. It can also trick Windows system features into launching hidden scripts.
| Name | STX remote access trojan |
| Threat Type | Remote Administration Trojan (RAT) |
| Detection Names | Avast (MalwareX-gen [Trj]), Combo Cleaner (Gen:Variant.StxRat.1), ESET-NOD32 (Win64/Agent.IJZ Trojan), Kaspersky (HEUR:Trojan.Win64.OutPack.gen), Microsoft (Trojan:Win32/Egairtigado!rfn), Full List (VirusTotal) |
| Symptoms | RATs are designed to stealthily infiltrate the victim's computer and remain silent, and thus no particular symptoms are clearly visible on an infected machine. |
| Possible distribution methods | Compromised websites, malicious links, infected installers. |
| Damage | Stolen passwords and banking information, identity theft, the victim's computer added to a botnet, additional infections, financial loss. |
| Malware Removal (Windows) |
To eliminate possible malware infections, scan your computer with legitimate antivirus software. Our security researchers recommend using Combo Cleaner. Download Combo CleanerTo use full-featured product, you have to purchase a license for Combo Cleaner. 7 days free trial available. Combo Cleaner is owned and operated by RCS LT, the parent company of PCRisk.com. |
Conclusion
STX is malware designed to avoid detection and stay hidden on infected systems. It checks for virtual machines, debuggers, and security tools, and exits if it detects analysis. Once active, it can steal passwords and other sensitive data and give attackers remote control of the device.
Victims of STX attacks may have their devices infected with more malware, have personal data or money stolen, have their accounts hijacked, and encounter other issues. If detected on a device, the RAT should be removed immediately. Here are more examples of RATs: AtlasCross, CrySome, and CrystalX.
How did STX infiltrate my computer?
It is known that STX was delivered using a compromised CPUID website where legitimate download links were replaced with malicious ones. Users who downloaded and executed the infected installers unknowingly run the RAT on their devices. The malware was hidden within legitimate programs, using a technique that tricks Windows into running a malicious DLL.
Threat actors were also observed using a VBScript downloaded from a browser, which ran a JScript file to download and extract an archive containing STX. The archive contained the malware and a PowerShell loader that ran it directly in memory to avoid detection. This RAT was also spread via fake FileZilla download sites that hosted infected installers.
How to avoid installation of malware?
Only download software from official websites or trusted app stores, and stay away from pirated programs, cracks, or key generators. Keep your operating system and applications updated to the latest versions.
Be cautious with unexpected emails or messages, especially from unknown senders that include links or attachments. If anything looks suspicious, avoid opening it. Do not click on pop-ups, ads, or prompts from untrusted websites, and never allow notifications from questionable pages.
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.
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.
Disconnect from the network
Unplug your Ethernet cable and turn off Wi-Fi. If you're on a laptop, the airplane-mode key works fastest.
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.
Boot into Safe Mode with Networking
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.
Open . Click Restart now next to Advanced startup.
Your computer will restart into the "Choose an option" menu. Click . After the second reboot, press 5 or F5.
Click the Windows logo, hold Shift, click the Power icon and choose Restart. In the Choose an option screen, click . 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.
Inspect running processes with Process Explorer
Download Process Explorer from Microsoft Sysinternals. Run it as Administrator. Click and .
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.
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.
Map every persistence point with Autoruns
Download Autoruns. Right-click Autoruns.exe and choose Run as administrator - without elevation, Autoruns can't inspect protected registry hives.
In the menu, open and , 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
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.
Check the hosts file and DNS settings
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 and verify both DNS and DNS over HTTPS (DoH) settings haven't been hijacked.
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.
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.
Run Microsoft Defender Offline
Reboot to normal Windows. Open . 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.
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.
VB100 certified. Includes anti-trojan, registry/persistence scanning, anti-spyware in one pass. The 7-day free trial is available.
Download Combo CleanerRun Combo Cleaner full system scan
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.
Run Microsoft Safety Scanner as a second-opinion scan
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.
Different scanning engines catch different threats. Running an additional Microsoft scan after Combo Cleaner is the single most underused verification step in malware removal.
Manually remove anything still listed in Autoruns
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.
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).
Reset browsers and clear notification permissions
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/resetand click "Restore settings to their original defaults." Then visitchrome://settings/content/notificationsand remove any unfamiliar sites. - Edge: visit
edge://settings/reset. Then checkedge://settings/content/notifications. - Firefox: open
about:supportand 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.
Re-enable Defender, Tamper Protection, and update everything
Many trojans disable security software. Open 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 () and update your browsers and applications. The infection vector that let the trojan in originally usually involves outdated software.
Change passwords from a clean device
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:
- Primary email first - it's the recovery hub for everything else
- Banking and financial accounts
- Password manager master password (if you use one)
- 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.
Verify the clean and monitor for 7 days
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 . 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 device is infected with STX malware, should I format my storage device to get rid of it?
Doing so will remove STX completely, but it will also deletes all data on the device. It is usually better to try a trusted anti-malware tool like Combo Cleaner first before taking more drastic steps.
What are the biggest issues that malware can cause?
Malware can steal sensitive information, encrypt files, download additional malicious software, and carry out other harmful actions. This may lead to financial loss, identity theft, unauthorized access to accounts or devices, and even permanent data loss.
What is the purpose of STX?
STX can steal passwords, cookies, information from crypto wallets, and other sensitive data. It also allows attackers to remotely control the device and launch additional attacks by downloading and running additional malware.
How did STX infiltrate my computer?
STX was spread through compromised and fake software download sites as well as malicious scripts. Users activated it by running infected installers or files disguised as legitimate programs. It was delivered using techniques that hide the malware inside seemingly legitimate software.
Will Combo Cleaner protect me from malware?
Yes, Combo Cleaner is able to detect and remove many threats. However, more advanced malware can sometimes hide deeper in the system, so running a full system scan is highly recommended.
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Tomas Meskauskas
Expert security researcher, professional malware analyst
I am passionate about computer security and technology. I have an experience of over 10 years working in various companies related to computer technical issue solving and Internet security. I have been working as an author and editor for pcrisk.com since 2010. Follow me on Twitter and LinkedIn to stay informed about the latest online security threats.
PCrisk security portal is brought by a company RCS LT.
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DonatePCrisk security portal is brought by a company RCS LT.
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