Is it a Virus?
✔ NO - Safe
Must be in C:\Windows\System32\drivers\fastfat.sys
Warning
Driver loaded during FAT volume access
Loaded by the NT kernel when FAT volumes are mounted
Can I Disable?
✔ YES
Disabling is not recommended; Windows requires FAT support for FAT volumes
What is fastfat.sys?
FASTFat.sys is the Windows FAT file system driver. It is a kernel-mode component loaded by the NT kernel to mount, read, write, and manage FAT-formatted volumes such as FAT32 USB drives and SD cards.
FASTFat.sys runs in kernel space and implements FAT IO operations, caching, and metadata handling for FAT volumes. It ensures compatibility with FAT media while isolating operations from user-mode processes.
Quick Fact: FASTFat.sys is a long-standing Windows driver introduced to support FAT volumes and maintain compatibility with removable media.
Types of FASTFat Roles
- Kernel Driver: The primary fastfat.sys kernel-mode driver handling FAT IO requests.
- Volume Mount Handler: Responsible for mounting and unmounting FAT-formatted volumes.
- Cache and Metadata Manager: Manages file data caching and directory metadata for FAT volumes.
- Error Reporting: Reports and logs errors related to FAT IO operations.
- Disk Access Synchronizer: Synchronizes access to FAT-formatted disks with the OS scheduler.
Is fastfat.sys Safe?
Yes, fastfat.sys is safe when it is the legitimate Microsoft file located in the Windows drivers folder.
Is fastfat.sys a Virus or Malware?
The real fastfat.sys is not a virus, but malware may masquerade with similar names. Always verify the file path and signature.
How to Tell if fastfat.sys is Legitimate or Malware
- File Location: Must be in
C:\Windows\System32\drivers\fastfat.sys. Any fastfat.sys elsewhere is suspicious.
- Digital Signature: Right-click the file in File Explorer → Properties → Digital Signatures. Should show "Microsoft Corporation" as signer.
- File Version: Check details in Properties → Details for a valid system driver version (e.g., 10.x.x.x) signed by Microsoft.
- Behavior: Driver should only load when FAT volumes are accessed; persistent behavior outside this context is suspicious.
Red Flags: If fastfat.sys is not in the Windows drivers folder, lacks a valid Microsoft signature, or causes unusual high IO when no FAT volumes are mounted, scan with Windows Defender or your security tool.
Why Is fastfat.sys Running on My PC?
fastfat.sys runs as part of the Windows FAT volume support whenever a FAT-formatted disk or USB drive is connected or mounted.
Reasons it's running:
- Active FAT Volume Access: A FAT-formatted drive is mounted or accessed by the OS or applications.
- Background Cache Operations: The driver may perform caching and metadata updates in the background for performance.
- Volume Mount/Unmount Events: Mounting or unmounting FAT volumes triggers the driver's load and unload cycles.
- Boot-Time Volume Support: On startup, Windows probes for boot or system FAT volumes and loads the driver if needed.
- Removable Media Insertion: Inserting a USB flash drive with a FAT32/ FAT16 partition triggers the driver for access.
Can I Disable or Remove fastfat.sys?
Do not disable fastfat.sys. It is part of Windows FAT support and required for FAT volumes. Disabling may cause system instability or inaccessibility of FAT media.
How to Stop fastfat.sys
- End Active FAT IO: Safely eject FAT media and close applications using it; there is no straightforward task to stop the kernel driver from Task Manager.
- Disable FAT Media Mounting: In general, Windows manages mounting; there is no simple switch to disable fastfat.sys per se.
- Safe Mode: If you suspect issues, boot into Safe Mode to limit driver loading.
- System Configuration: Use Msconfig or Task Manager's Startup tab to minimize disk-related services; removing core drivers is not recommended.
- System Policy: For enterprise environments, consult IT to adjust policy or registry safely without breaking system integrity.
How to Uninstall FASTFat (Not Recommended)
- ✔ You should not uninstall core Windows drivers; FASTFat is part of the OS FAT support.
- ✔ In rare cases, a Windows Feature or optional component enabling FAT support may be altered, but this is not typical for consumer systems.
Common Problems: FAT Driver Issues
If fastfat.sys is causing problems such as hangs, high IO, or failed FAT volume mounts, try the following actions.
Common Causes & Solutions
- Corrupted FAT Volume: Run CHKDSK /F on the affected drive and consider restoring from backup.
- Outdated Windows Version: Install the latest Windows updates to ensure FAT driver fixes are applied.
- Conflict with USB Disk Utilities: Disable third-party USB tools or disk management software that may interfere with the driver.
- Mass Storage Devices with Nonstandard FAT: Verify the device format (FAT32/FAT16) and try another USB port or device.
- Driver Cache Corruption: Restart the system to reinitialize the FAT driver cache and perform disk checks.
- Unmounted Volume Remains Locked: Use a proper ejection method and restart if needed; avoid force-dismounts on open files.
Quick Fixes:
1. Run CHKDSK on the affected drive
2. Safely eject and replug FAT media
3. Update Windows to the latest build
4. Disable conflicting USB disk utilities
5. Run System File Checker: sfc /scannow
Frequently Asked Questions
What is fastfat.sys?
FASTFat.sys is the Windows FAT file system driver. It enables Windows to mount and operate FAT-formatted volumes like USB drives and memory cards.
Is fastfat.sys safe?
Yes, when located in C:\Windows\System32\drivers and signed by Microsoft; as with any driver, ensure authenticity to avoid spoofed files.
Where is fastfat.sys located?
C:\Windows\System32\drivers\fastfat.sys is the standard location on Windows systems.
Can I disable fastfat.sys?
Disabling is not recommended because FAT support is required for removable media on many systems; only enterprise configurations with alternative media formats may modify this.
What problems can fastfat.sys cause?
Issues typically involve failed FAT volume mounts, IO errors on USB drives, or rare driver conflicts; update Windows and scan for malware if suspected.
How do I fix a fastfat.sys blue screen?
Boot to Safe Mode, run sfc /scannow, update drivers, run CHKDSK, and consider repairing the system image using DISM if needed.