What is NaiFiltr?

The genuine NaiFiltr.sys file is a software component of McAfee On-Access File Scanner by McAfee.
NaiFiltr.sys is a filter driver that belongs to the McAfee On-Access File Scanner, a program that scans files as they are opened or run by the user. A filter driver is a software program that adds functionality to peripheral devices. It can even add support for a specialized device in the computer. This driver is an important part of the McAfee Virus Scan and removing it may cause the program to malfunction. The McAfee On-Access File Scanner (OAS) has since been integrated into the McAfee VirusScan and McAfee Endpoint Security. The OAS service prevents threats by scanning for viruses spyware while letting users select the kind of files needed to be scanned, what network drives to scan from, and maximum scan time of the application. OAS has been known to be a resource hog but can easily be disabled through the parent program. McAfee, Inc. (formerly Network Associates Inc.) is the world's largest company dedicated solely to the development and distribution of security software. It is headquartered in Santa Clara, California, USA. McAfee was founded in 1987 by John McAfee, who later left the company in 1994. Intel bought over McAfee on February 28, 2011 for $7.68 billion.

NAIFiltr stands for Network Associates Incorporated Filter Driver

NaiFiltr.sys is a Windows driver. A driver is a small software program that allows your computer to communicate with hardware or connected devices. This means that a driver has direct access to the internals of the operating system, hardware etc. The free file information forum can help you determine if NaiFiltr.sys is a Windows system file or if it belongs to an application that you can trust.

Run a free scan to check for NaiFiltr drivers in need of updating

NaiFiltr.sys file information

The process known as NaiFiltr Device Driver belongs to software McAfee On-Access Scanner or NaiFiltr by Network Associates (

Description: NaiFiltr.sys is not essential for the Windows OS and causes relatively few problems. NaiFiltr.sys is located in the C:\Windows\System32\drivers folder. Known file sizes on Windows 10/8/7/XP are 23,296 bytes (66% of all occurrences) or 23,888 bytes. 
The driver can be started or stopped from Services in the Control Panel or by other programs. The program has no visible window. The file is a Microsoft signed file. The NaiFiltr.sys file is not a Windows system file. NaiFiltr.sys appears to be a compressed file. Therefore the technical security rating is 2% dangerous, however you should also read the user reviews.

Recommended: Identify NaiFiltr.sys related errors

If NaiFiltr.sys is located in a subfolder of "C:\Program Files\Common Files", the security rating is 24% dangerous. The file size is 24,480 bytes. You can uninstall this program in the Control Panel. The program has no visible window. There is no detailed description of this service. NaiFiltr.sys is not a Windows core file. NaiFiltr.sys appears to be a compressed file.

Uninstalling this variant: If there are any problems with NaiFiltr.sys, you can also uninstall McAfee VirusScan software via Windows Control Panel/Add or Remove Programs (Windows XP) or Programs and Features (Windows 10/8/7).

Important: Some malware disguises itself as NaiFiltr.sys, particularly when not located in the C:\Windows\System32\drivers folder. Therefore, you should check the NaiFiltr.sys process on your PC to see if it is a threat. We recommend Security Task Manager for verifying your computer's security. This was one of the Top Download Picks of The Washington Post and PC World.


User Comments

This is a driver for McAfee Antivirus scanning engine
Caused a crash (Bluescreen) on my Win XP System!
crashed at least once per hour! Error = NaiFiltr.SYS is missing. McAfee are NO help
I think this is a McAffee Firewall file
I believe its connected to my freezing problem, and USB [adildr.sys] failing to start. which happens at the same time.
Bad programming from McAfee
this program periodically causes bluescreen errors on older computers
  Mcafee troubleshooting  
it is a mcafee problem
Caused a persistant blue screen upon start up and prevented further access to Windows XP

Rating chart

Summary: Average user rating of NaiFiltr.sys: based on 10 votes with 9 user comments. 7 users think NaiFiltr.sys is essential for Windows or an installed application. 2 users think it's probably harmless. One user thinks it's neither essential nor dangerous. One user is not sure about it.

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Best practices for resolving NaiFiltr issues

A clean and tidy computer is the key requirement for avoiding problems with NaiFiltr. This means running a scan for malware, cleaning your hard drive using cleanmgr and sfc /scannow, uninstalling programs that you no longer need, checking for Autostart programs (using msconfig) and enabling Windows' Automatic Update. Always remember to perform periodic backups, or at least to set restore points.

Should you experience an actual problem, try to recall the last thing you did, or the last thing you installed before the problem appeared for the first time. Use the resmon command to identify the processes that are causing your problem. Even for serious problems, rather than reinstalling Windows, you are better off repairing of your installation or, for Windows 8 and later versions, executing the DISM.exe /Online /Cleanup-image /Restorehealth command. This allows you to repair the operating system without losing data.

To help you analyze the NaiFiltr.sys process on your computer, the following programs have proven to be helpful: Security Task Manager displays all running Windows tasks, including embedded hidden processes, such as keyboard and browser monitoring or Autostart entries. A unique security risk rating indicates the likelihood of the process being potential spyware, malware or a Trojan. Malwarebytes Anti-Malware detects and removes sleeping spyware, adware, Trojans, keyloggers, malware and trackers from your hard drive.

Other processes

NaiFiltr.sys [all]