Default browser keep popping up with random sites

Question

I have recently noticed my computer run a looks like quick cmd prompt upon startup my pc and after that the default browser (no matter edge or google) is suddenly open (in this case into some random sites mostly shopping or gambling) usually 2 tab sometime only 1 tab.

I have tried looking through installed app and start up program and found nothing unusual and tried all the scan option through windows defender, tried the 3rd party such as malwarbyte, adwcleaner and emisoft and the problem still persist even after showing no detection in scan.

I used those third party due to my assumption this is a malware although I have no knowledge in such matter, I have never experience this before and I don't really know how bad is it gonna be to my pc due to some personal information in it, therefore any solution and help to understand it would be appreciated

Answer 1

The behavior described is consistent with a browser‑hijacking or adware component that is not being caught by standard scans, or with repeatedly visiting a malicious/compromised site that keeps triggering pop‑ups and redirects.

To reduce the risk and further clean up the system, follow these steps:

1. Run a full Microsoft Defender scan from Windows Security
   • Open Windows Security → Virus & threat protection.
   • Select Scan options → Full scan and let it complete.
   • If the problem keeps returning, run Microsoft Defender Offline for a deeper scan:
     • In Virus & threat protection, select Scan options.
     • Choose Windows Defender Offline scan → Scan now. The PC will restart and scan outside Windows to catch hidden threats.
2. Avoid sites and content that may be re‑infecting the browser
   • Avoid sites that provide illegal downloads or pirated content, and any site that aggressively opens pop‑ups or redirects, especially gambling or “free” streaming/download sites.
   • Use a modern browser like Microsoft Edge with Microsoft Defender SmartScreen enabled to help block malicious or compromised sites.
3. Watch for signs of deeper malware
   • If the PC is unusually slow, crashes, shows constant unexpected pop‑ups, or cannot open security‑related sites (like Windows Update or security pages), treat this as a strong sign of malware and continue using Microsoft’s security tools.
4. General protection steps
   • Keep Windows and all software updated via Windows Update to get the latest security fixes.
   • Use only one real‑time anti‑malware product at a time to avoid instability; Microsoft Defender is included with Windows and kept updated automatically.
   • Be cautious with email attachments and links, especially from unfamiliar senders.

If, after a Microsoft Defender Offline scan and avoiding risky sites, the random tabs still appear, the next steps would typically be:

• Remove any unfamiliar or unneeded browser extensions.
• Reset the browser settings to default.
• Review scheduled tasks and startup entries for unknown items (and remove only those that are clearly unwanted).

---

References:

• How to start a scan for viruses or malware in Microsoft Defender
• Troubleshoot problems with detecting and removing malware
• Microsoft resources and guidance for removal of malware and viruses
• Prevent malware infection
• Protect my PC from viruses