How To Check For Malware On Pc – Full System Antivirus Scan

by

A slow or suspicious PC often benefits from a thorough check for unwanted malware. If you’re wondering how to check for malware on pc, you’re taking the right first step towards securing your system. This guide provides clear, step-by-step methods to identify and remove malicious software, from using built-in tools to advanced manual techniques.

How To Check For Malware On Pc

Checking your computer for malware is a systematic process. You don’t need to be a tech expert to perform a basic scan, but understanding the different approaches ensures a more comprehensive check. We’ll start with the simplest methods and progress to more detailed procedures.

Use Built-In Windows Security

Windows 10 and 11 come with a robust, free antivirus solution called Microsoft Defender Antivirus. It runs in the background, but initiating a manual scan is straightforward.

  1. Open the Start menu and type “Windows Security,” then select the app.
  2. Click on “Virus & threat protection.”
  3. Under “Current threats,” click “Scan options.”
  4. Choose a scan type. A “Quick scan” checks common areas, while a “Full scan” examines every file and running program. For a thorough check, select “Full scan.”
  5. Click “Scan now.” The process can take an hour or more depending on your storage.

Remember to check for updates before scanning. In the Windows Security app, go to “Virus & threat protection” settings and click “Check for updates” under “Protection updates.” An outdated virus database won’t catch the latest threats.

Perform A Scan With A Dedicated Antivirus Program

While Windows Defender is competent, using a second opinion scanner or a full third-party suite can detect malware it might miss. Many reputable companies offer free versions.

  • Download a trusted scanner like Malwarebytes, Bitdefender Free, or Kaspersky Security Scan from the official website only.
  • Install the software, ensuring you deselect any optional offers for other software during setup.
  • Update its virus definitions immediately after installation.
  • Run a full system scan. Do not use your PC for other tasks during this scan for best results.
  • Review the scan results and follow the software’s prompts to quarantine or remove any detected items.

It’s generally not advisable to run two real-time antivirus programs simultaneously as they can conflict. Use one as your primary protector and others as on-demand scanners.

Understanding Quarantine Versus Removal

When antivirus software finds a threat, it typically gives you two options: quarantine or remove. Quarantine isolates the file in a secure folder, preventing it from running but keeping it on your disk. This is useful if the software flags a legitimate file by mistake. Removal deletes the file permanently. For confirmed malware, always choose removal.

Check For Symptoms Of Malware Infection

Sometimes, signs of infection appear before any scanner detects them. Knowing these symptoms can prompt you to run a check.

  • Extremely slow performance, especially when opening programs or browsing.
  • A sudden onslaught of pop-up ads, even when you’re not using a web browser.
  • Your web browser’s homepage has changed without your permission, or you have new toolbars or extensions.
  • Frequent system crashes, the infamous Blue Screen of Death (BSOD), or programs freezing.
  • Unusual network activity, like your internet slowing to a crawl for no apparent reason.
  • Security software or Task Manager being disabled or blocked from opening.
  • Files disappearing, being encrypted, or strange new files appearing.
  • Unexplained spikes in CPU or memory usage in Task Manager.

Monitor Task Manager For Suspicious Activity

Windows Task Manager is a powerful buildt-in tool for spotting malware processes. Press Ctrl + Shift + Esc to open it.

  1. Click on the “Processes” tab. Sort by “CPU” or “Memory” by clicking the column header.
  2. Look for processes with suspicious or misspelled names, or those using high resources when you’re not running any programs.
  3. Be cautious. Some legitimate processes from Microsoft or your hardware manufacturer may have unfamiliar names. Right-click on a suspicious process and select “Search online” to investigate before ending it.
  4. If you identify a confirmed malicious process, right-click it and select “End task.” Note that sophisticated malware may restart itself.

Also check the “Startup” tab. Malware often registers itself to launch when Windows starts. Disable any entries you don’t recognize or trust.

Review Your Browser Extensions And Add-Ons

Browser hijackers and adware often install through extensions. Check each browser you use.

  • In Google Chrome: Go to Settings > Extensions.
  • In Mozilla Firefox: Go to Add-ons and Themes > Extensions.
  • In Microsoft Edge: Go to Settings > Extensions.

Remove any extensions you did not knowingly install or no longer use. Pay close attention to extensions that claim to offer shopping assistance, PDF converters, or search enhancers, as these are common culprits.

Check Your Network Connections

Malware sometimes communicates with external servers. You can view active connections using the Command Prompt.

  1. Type “cmd” in the Start menu, right-click “Command Prompt,” and select “Run as administrator.”
  2. Type the command netstat -ano and press Enter. This lists all active connections and the Process ID (PID) using them.
  3. Look for connections to strange IP addresses, especially if they show a state of “ESTABLISHED.” Note the PID.
  4. Go back to Task Manager, enable the “PID” column (right-click headers > Select columns), and find the process matching that PID to identify the program.

Advanced Manual Check Procedures

If scans and basic checks haven’t resolved the issue, or you still suspect an infection, these advanced steps can help.

Run Scans In Safe Mode

Safe Mode starts Windows with only the essential drivers and services. This prevents most malware from loading, making it easier for security software to find and remove it.

  1. Click the Start button, then the Power icon.
  2. Hold down the Shift key and click “Restart.”
  3. After restart, select “Troubleshoot” > “Advanced options” > “Startup Settings” > “Restart.”
  4. When your PC restarts again, press the 4 or F4 key to enable Safe Mode.
  5. Once in Safe Mode, run a full scan with your primary antivirus and a secondary scanner like Malwarebytes.

Use Windows Defender Offline Scan

This is a powerful tool for removing persistent malware that hides from scanners running within Windows. It runs from a trusted environment before Windows boots.

  1. Open Windows Security > Virus & threat protection.
  2. Under “Current threats,” click “Scan options.”
  3. Select “Microsoft Defender Offline scan” and click “Scan now.”
  4. Your PC will save your work and restart. The scan, which takes about 15 minutes, will run automatically.

Analyze System Files With SFC And DISM

Malware can corrupt critical Windows system files. Windows includes utilities to repair them.

First, run the System File Checker (SFC):

  1. Open an Administrator Command Prompt as described earlier.
  2. Type sfc /scannow and press Enter. The tool will scan and attempt to repair protected system files.

If SFC finds problems it cannot fix, use the Deployment Image Servicing and Management (DISM) tool:

  1. In the same Command Prompt, type DISM /Online /Cleanup-Image /RestoreHealth and press Enter.
  2. This process uses Windows Update to source replacement files and can take 10-20 minutes.

Post-Check Actions And Prevention

After checking for and removing malware, follow these steps to secure your system and prevent future infections.

Change Your Passwords

If you had a malware infection, especially a keylogger or information stealer, assume your passwords are compromised. This is crucial for email, banking, and social media accounts. Use a strong, unique password for each site. Consider using a reputable password manager to generate and store them.

Update Your Software

Outdated software, especially your operating system, browser, and plugins like Java or Adobe Flash (if still used), are major security holes. Enable automatic updates in Windows Settings under “Windows Update.” Regularly check for updates for other programs you use frequently.

Review System Restore Points

Malware can sometimes infect System Restore points. To be safe, you can turn System Restore off and on to clear existing points after cleaning your PC.

  1. Type “Create a restore point” in the Start menu and select the result.
  2. Select your main drive (usually C:) and click “Configure.”
  3. Click “Disable system protection,” then “Apply.”
  4. Repeat, but re-enable protection and click “Create” to make a new, clean restore point.

Maintain Ongoing Protection Habits

  • Enable real-time protection in your antivirus software and keep it updated.
  • Be cautious with email attachments and links, even from known senders.
  • Only download software from official vendor websites or trusted app stores.
  • Use an ad-blocker in your web browser to reduce exposure to malvertising.
  • Regularly back up your important files to an external drive or cloud service. This is your final defense against ransomware.

Frequently Asked Questions

How Can I Check For Malware On My PC For Free?

You can perform a comprehensive free check using Windows Defender for a full system scan, supplemented by free on-demand scanners like Malwarebytes. The manual checks using Task Manager, browser extensions, and network connections are also completely free and built into Windows.

What Are The Signs Your Computer Has A Virus?

Common signs include a significant slowdown in performance, constant pop-up advertisements, changes to your browser homepage or search engine, programs crashing frequently, and unexpected high CPU or network usage visible in Task Manager. Unfamiliar programs starting with Windows is another red flag.

How Do I Run A Malware Scan On Windows 10?

Open Windows Security from the Start menu, go to “Virus & threat protection,” and click “Scan options.” Select “Full scan” for the most thorough check and click “Scan now.” Ensure your virus definitions are updated before starting the scan for the best results.

Can Malware Hide From Antivirus Software?

Yes, sophisticated malware like rootkits can sometimes hide from standard antivirus scans. This is why using specialized tools like the Windows Defender Offline scan or bootable antivirus rescue media from a USB drive can be effective, as they run outside the normal operating system where malware operates.

How Often Should I Check My PC For Malware?

With real-time protection enabled, your antivirus is constantly checking. You should schedule a manual full system scan at least once a month. Perform an immediate scan if you notice any suspicious system behavior, accidentally click a dubious link, or install software from an untrusted source.