A sluggish computer or a sudden barrage of pop-ups is a critical security alert. Malicious software can silently compromise your company's sensitive data, disrupt entire networks, and inflict significant financial damage. For IT professionals and enterprise environments, knowing precisely how to check for malware on a computer is a foundational skill. This guide provides clear, actionable methods to identify and address threats on your Windows systems, safeguarding your digital assets and maintaining operational integrity.
Recognizing the early warning signs of malware
The first line of defense is often observation. While some malware is designed to be invisible, many infections produce noticeable side effects on a computer's performance and behavior.
Performance issues and unexplained slowdowns
A sudden and unexplained slowdown is one of the most common indicators. If routine tasks like opening applications or booting up the system take significantly more time, malware could be consuming system resources in the background.
Unwanted pop-ups and browser changes
Another classic sign is the appearance of unexpected pop-up advertisements, warnings, or messages. These can appear even when you are not browsing the internet and are often designed to trick you into installing more malicious software or divulging personal information. Similarly, if your browser's homepage or default search engine changes without your consent, it's a strong red flag.
System instability and unauthorized programs
System instability, such as frequent crashes or the infamous "Blue Screen of Death" (BSOD) in Windows, can also point to a malware infection. Malicious code can interfere with critical system files and processes, leading to conflicts that cause the operating system to fail. You may also notice new, unfamiliar icons on your desktop or applications installed that you don't remember authorizing.
Suspicious network activity
Pay close attention to network activity. A spike in internet usage when the computer should be idle could indicate that malware is communicating with a remote server, sending your data, or using your device as part of a botnet. Monitoring these signs allows IT teams to intervene early, before a minor infection escalates into a major security breach.
How to check for malware on your computer using built-in Windows tools
Both Windows 11 and Windows 10 come equipped with a powerful, integrated security solution: Microsoft Defender Antivirus. This tool provides real-time protection and offers multiple scanning options to help you find and remove threats from your device. For most organizations, this is the primary tool for routine security checks.
To initiate a scan, you need to access the Windows Security center. The process is straightforward and provides IT professionals with the control needed to manage device security effectively. Microsoft Defender is a robust first line of defense against common viruses and other malicious software.
Here is how to check for malware on your computer using this built-in utility. The following steps apply to both Windows 11 and Windows 10, with minor differences in the user interface.
Open Windows Security: Go to Settings > Privacy & security > Windows Security. Alternatively, you can search for "Windows Security" in the Start Menu and select the app.
Navigate to virus & threat protection: In the Windows Security dashboard, select the Virus & threat protection option.
Choose a scan option: Under the "Current threats" section, you will see Scan options. Click this to view the different types of scans available.
- Quick scan: Checks the folders and files where threats are most commonly found.
- Full scan: Checks every file and running program on your hard disk. This can take a significant amount of time, often over an hour.
- Custom scan: Allows you to select specific files and folders to scan.
- Microsoft Defender Offline scan: Restarts your computer and runs a deep scan before the full Windows operating system loads. This is highly effective for removing persistent malware that is difficult to detect while Windows is running.
Start the scan and review results: Select the scan you wish to run and click Scan now. After the scan is complete, you can review the Protection History to see any threats that were found and the actions Defender took.
For IT administrators managing multiple accounts and devices, regularly running a full scan or an offline scan is a critical security measure. The Protection History provides a valuable log for compliance and incident response, showing what was detected on each device and when.
Leveraging third-party anti-malware solutions
While Microsoft Defender provides excellent baseline protection, many organizations adopt a defense-in-depth strategy. This involves using a secondary, third-party anti-malware tool to get a second opinion. No single security product can catch 100% of threats, and using multiple layers of defense significantly improves your chances of detecting sophisticated malware.
Real-time protection vs. on-demand scanning
It's important to distinguish between real-time antivirus protection and on-demand scanners. You should only have one real-time anti-virus program running at a time to avoid system conflicts. However, you can safely use on-demand scanners alongside Microsoft Defender. These tools do not run constantly in the background; you launch them manually to perform a scan when needed.
Choosing reputable tools and vendors
Many reputable cybersecurity companies offer free or paid on-demand scanners. These tools are useful for periodic deep-dives or for confirming a suspected infection that your primary antivirus may have missed. When selecting a tool, ensure it comes from a well-known and trusted developer to avoid inadvertently installing a fake or malicious program.
Enterprise-grade endpoint protection
For enterprise environments, centrally managed endpoint detection and response (EDR) solutions offer advanced capabilities beyond simple scanning. These platforms provide greater visibility into endpoint activity, threat hunting features, and automated response actions, offering a higher level of security and support for IT teams managing a large fleet of devices.
Key takeaways for proactive system security
Effectively checking for malware is a combination of using the right tools and adopting a proactive security mindset. Your primary goal should be to prevent infections before they happen. This involves keeping your Windows operating system, your web browsers, and all other software fully updated. Software updates frequently contain critical security patches that close vulnerabilities exploited by malware.
Educating users about safe computing practices is equally important. This includes training them to recognize phishing emails, avoid suspicious downloads, and use strong, unique passwords for every account. A security-aware workforce is one of the most effective defenses against malware that relies on social engineering to spread. You must manage user accounts and permissions carefully to limit the potential damage an infection can cause.
For IT professionals managing a distributed workforce, maintaining system security across remote devices presents a unique challenge. This is where secure remote access becomes indispensable. A platform built on security, like TeamViewer, allows IT teams to connect to any device, anywhere, to run malware scans, install security updates, and manage system settings without disrupting the end-user. This capability ensures that security protocols are consistently applied across the entire organization, regardless of physical location. Seamless remote access empowers IT to respond to security alerts in real time, isolating a potential threat before it can spread.