The Tool Desk
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What a keylogger can capture—and why symptoms are unreliable
A keylogger is malware that records what you type. Microsoft’s description of the Win32/Keylogger family says it can collect keystrokes, emails, messages, application activity, logon sessions, and information entered into forms, then send sensitive information to an attacker. Microsoft’s threat description lists these capabilities, but they should not be taken to mean every keylogger behaves identically.
There is no dependable symptom checklist that can confirm or rule out an infection. A slow computer, unusual activity, or no obvious change does not establish whether a keylogger is present. Microsoft notes that an alert from security software may be the only symptom. A scan is more useful than trying to diagnose the problem by appearance, though no scan result guarantees that every threat has been found.
How to scan a Windows PC for a keylogger
1. Update antimalware definitions and run a full scan
On Windows, begin with Microsoft Defender Antivirus or your installed antimalware product: update its security intelligence, then run a full scan and follow any quarantine or removal prompts. Microsoft’s Win32/Keylogger entry says Defender Antivirus detects and removes that listed threat family. That is a specific vendor entry, not a promise that a scan will detect every new or customized keylogger.
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2. Run Microsoft Defender Offline if needed
If concern remains, consider Microsoft Defender Offline. Microsoft describes it as scanning from a trusted environment outside the normal Windows kernel, which can help when malware may interfere with scanning inside Windows. Check Microsoft’s current supported platforms and prerequisites before starting: Microsoft Defender Offline scan in Windows.
Some configurations require additional preparation. Microsoft notes that BitLocker users may need to suspend protection or provide a recovery key. Follow the instructions for your Windows version and chosen workflow; firmware changes or bootable USB media are not necessary for every setup.
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3. Use Microsoft Safety Scanner for a manually triggered check
Microsoft Safety Scanner is a Windows tool that you download and run manually to find and remove malware. It does not provide continuous, real-time protection; Microsoft recommends Defender Antivirus for real-time protection with automatic updates. Check the tool’s current details and download it from Microsoft Safety Scanner Download.
4. Treat a clean scan as useful evidence, not proof
A scan that finds nothing is reassuring but does not prove the device is clean. Microsoft explains that rootkits can hide malware and alter what a device reports about itself. If alerts continue, the problem persists, or you have reason to believe the compromise is severe, get help from a qualified technician or consider restoring the PC from a clean, uninfected copy. Microsoft’s rootkit overview explains why some threats can be difficult to see.
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- Contain and remove the threat. Follow the security tool’s quarantine or removal instructions. Avoid entering passwords or other sensitive information on the suspected PC until you have addressed the detection.
- Change exposed passwords from a clean device. Use a different device you believe is not compromised, such as a fully updated phone or another computer. Prioritize email, financial, work, and other important accounts, and enable multifactor authentication where available. Microsoft’s keylogger guidance advises changing passwords after removal: Win32/Keylogger threat description.
- Consider restoration for a severe compromise. If the infection cannot be removed confidently or the device remains compromised, restoration from a clean, uninfected copy may be necessary. Microsoft’s guidance for a documented keylogger Trojan discusses this option: TrojanSpy:Win32/Keylogger threat description.
Do you need a USB drive for an offline scan?
Not necessarily. Microsoft Defender Offline can be launched through supported Windows workflows; removable media is an option for the specific workflow that calls for it, not a universal requirement. If you create offline scan media on a USB drive, back up its contents first: Microsoft says the process reformats the drive and recommends creating the media on an uninfected computer. Check the current instructions before proceeding at Microsoft Defender Offline scan in Windows.
What the available scans are for
| Option | Best suited to | Important distinction |
|---|---|---|
| Microsoft Defender Antivirus | Ongoing Windows protection and an initial full scan | Microsoft identifies it as the option for real-time protection with automatic updates. |
| Microsoft Defender Offline | A scan launched from a trusted environment outside the normal Windows kernel | Check supported platforms and prerequisites; some BitLocker setups may require protection suspension or a recovery key. USB media is only needed for workflows that use it, and creating it reformats the drive. |
| Microsoft Safety Scanner | A manual, on-demand malware scan | It scans only when manually run and is not a substitute for real-time protection. |
For current steps and requirements, use Microsoft’s pages for Defender Offline and Safety Scanner.
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What about macOS, iPhone, and Android?
The Microsoft procedures above apply to Windows. The available Microsoft guidance does not establish a matching keylogger-removal procedure for macOS or mobile devices, so do not assume these Windows steps or tools apply there. For another platform, use its built-in security guidance or contact the device maker or a qualified security professional; change potentially exposed account passwords from a separate, trusted device.
