How to Tell If You Have a Computer Virus

Do you have a virus or is something else going wrong?

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If you suspect your Windows desktop or laptop is infected with a virus or form of malware, there are two ways to verify it; locate the virus manually, or run multiple scans using a variety of reputable, security-based antivirus programs.

Do I Have a Virus: Signs of Infection

Not all viruses are similar, and some affect computer systems differently than others. In most cases, there are several visible warning signs to keep an eye on, like sluggish performance, odd pop-up dialog boxes, unexpected crashes, disabled antivirus tools, a different browser homepage, or a slow internet connection, to name a few.

In some situations, a PC virus won't cause any noticeable changes to your system. In this case, consistent scanning with a quality antivirus program is the only way to protect your computer. Knowing what symptoms to look out for is handy, but software and hardware issues often cause similar problems, hence why it's highly recommended to run multiple scans with different antivirus programs.

This article includes steps for Windows 7, 8, and 10.

How to Tell If Your Computer Has a Virus With Windows Task Manager

If you're not quite ready to scan your computer with antivirus software, reviewing Windows Task Manager for unusual or odd looking processes is an excellent place to begin. Some malware runs on startup and will attempt to disguise itself as a typically Windows process. With a quick Google search, you can quickly discern whether a process is legit, or something to investigate further.

Before monitoring your task manager, properly restart your PC via PowerShell or Command Prompt.

  1. Press Windows key+X, then select Windows PowerShell (Admin).

    A screenshot of the quick link menu in Windows 10.

    In Windows 7, press Windows key+R, enter "cmd," then select OK.

  2. Select Yes, when the UAC dialog appears.

    A screenshot of a Windows 10 UAC window.
  3. Enter the command "shutdown /r /t 0," then press Enter.

    A screenshot of PowerShell in Windows 10.
  4. With your PC restarted, right-click the taskbar, then select Task Manager.

    A screenshot of Windows' taskbar menu in Windows 10.
  5. Right-click a suspect process, then select Search online.

    A screenshot of the right-click menu of a running process in Windows' task manager.

    In Windows 7, copy the process name, then perform a manual search in your preferred web browser.

  6. Your default browser will open with Bing search results for that specific process.

    A screenshot of Bing's search results.

Read through multiple search results to ensure the process information is consistent.

Scan Computer for Virus With Windows Defender

Windows Defender was introduced with Windows 10 creator update and is the OS' built-in anti-malware application. Available for Windows 8 and 10, Windows Defender Antivirus is a tool worth utilizing if you think your computer is infected.

  1. Type "windows defender settings" into Windows search, then select Open once the results populate.

    A screenshot of Windows search in Windows 10.
  2. Select Virus & threat protection.

    A screenshot showing Windows Security options in Windows 10.
  3. Select Scan options.

    A screenshot of the Virus & threat protection options in Windows 10.
  4. Select one of the four scanning options — Quick scan, Full scan, Custom scan, Windows Defender Offline scan — then select Scan now.

    A screenshot showing the different virus scanning option in Windows Defender.

    Depending on the scan option you choose, it could take several minutes to complete. Performing an offline scan ensures your system is checked in a secure environment (similar to Safe Mode), rather than loading the full OS.

  5. Once the virus scan has finished, potential threats are listed above the scan details.

    A screenshot displaying the scan results in Windows Defender.
  6. If the scan reveals any potential threats, it's time to remove them now.

If you suspect your Android device has a virus, learn how to remove it.

How to Scan for Viruses on Windows 7 With Microsoft Security Essentials

Microsoft Security Essentials (MSE) offers real-time protection from malicious software and viruses on Windows 7. Using the same scanning engine and virus signature database as Windows Defender, MSE is a great place to begin if your PC is suffering from one or more of the warning signs previously mentioned.

Microsoft Security Essentials is free to download for Windows 7 Home users.

  1. Go to MSE's download page, choose your version (32 or 64-bit) and language, then click Save File.

    A screenshot of MSE's download page.
  2. Go to your Downloads folder, right-click mseinstall.exe, then click Run as administrator.

    A screenshot showing the right-click menu of a file in Windows 7.
  3. Click Next when the installation wizard appears.

    Ascreenshot of MSE's setup wizard.
  4. Review the Software License Terms, then click I accept.

    A screenshot of MSE's software license and terms.
  5. Choose one of the two Customer Experience Improvement options, then click Next.

    A screenshot of MSE's installation wizard.
  6. Select the options that apply (firewall and auto-sample submission), then click Next.

    A screenshot showing optimization options for MSE.

    If you don't have a firewall running, it's highly recommended to use the one included in MSE. The option to turn the firewall on or off is available after installation.

  7. Click Install.

    A screenshot of the final step in MSE's setup wizard.

    Make sure you uninstall any other antivirus programs on your system before you click Install.

  8. Click Scan my computer for potential threats after getting the latest updates, then click Finish.

    A screenshot confirming that MSE was installed.
  9. Allow MSE to update its virus and spyware definitions.

    A screenshot showing MSE updating its virus signatures.
  10. Once the virus signatures are updated, MSE will begin scanning your system.

    A screesnhot of a live scan in MSE on Windows 7.
  11. Once the scan is complete, any potentially harmful files or threats will be listed.

    A screenshot showing a completed virus scan in MSE.

To perform a more specific scan, select either Full or Custom in the right pane.

Perform a Malware Check Using Third-Party Antivirus Programs

Although Windows offers its own tools for virus and malware protection, it's always good practice to scan your system with a variety of antivirus software since each program has its own virus signature database.

A screenshot of AVG's download page.

In some cases, Windows might not flag a file, while other antivirus tools will, and vice-versa. Running multiple scans with different software providers is the best way to get an accurate picture of exactly what's going on. Fortunately, there are several free and paid antivirus tools to choose from.