What is kl1?

The genuine kl1.sys file is a software component of Kaspersky Anti-Virus by Kaspersky Lab.
The network driver for Kaspersky Antivirus, this file allows your operating system to communicate with the network hardware and enables the antivirus software to monitor traffic for malware. Initially released in 2006, Kaspersky Antivirus has won numerous awards and accolades for its success rate in detecting and eliminating spyware, viruses, and other malicious programs. Founded in 1997, Kaspersky is located in Moscow, Russia, and has offices in Boston and Miami.

KL1 stands for Kaspersky Lab 1 Unified Driver

Kl1.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 kl1.sys is a Windows system file or if it belongs to an application that you can trust.

Run a free scan to check for kl1 drivers in need of updating

Kl1.sys file information

The process known as Kaspersky Unified Driver or kl1 belongs to software Kaspersky Anti-Virus or The Shield Deluxe (version 2008) or Kaspersky Internet Security by Kaspersky Lab ( or Kaspersky Lab ZAO (

Description: Kl1.sys is not essential for the Windows OS and causes relatively few problems. Kl1.sys is located in the C:\Windows\System32\drivers folder. Known file sizes on Windows 10/8/7/XP are 128,016 bytes (41% of all occurrences), 110,360 bytes and 7 more variants. 
The driver can be started or stopped from Services in the Control Panel or by other programs. The program is not visible. The file is not a Windows system file. The service has no detailed description. Kl1.sys is a Verisign signed file. The file has a digital signature. kl1.sys appears to be a compressed file. Therefore the technical security rating is 12% dangerous, however you should also read the user reviews.

Uninstalling this variant: You could remove the entire program Kaspersky Internet Security or ZoneAlarm Antivirus using Windows Control Panel.

Recommended: Identify kl1.sys related errors

Important: Some malware disguises itself as kl1.sys, particularly when not located in the C:\Windows\System32\drivers folder. Therefore, you should check the kl1.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

Part of Kaspersky Anti-Virus Personal
I recently downloaded zonealarm security suite and noticed this file, after a quick browse i found that ZA is incorporating Kapersky into its scan software.
Main KAV 5.xx 6.xx Kernel Driver
  Whizard   (further information)
been getting Blue screens recently, even when Zonealarm turned off, kl1.sys and vsdatant.sys seem to be problem, hopefully uninstall works
Found file on my computer :C:\WINDOWS\SYSTEM32\ZoneLabs\avsys\instdrivers\x32.(Size: 110360 bytes) Used to be in "windows\system32\drivers" according to a registry scan. But not there anymore.
Kaspersky Unified Driver
With Zone Alarm Internet Security Suite 7.x the file is located in C:\WINDOWS\system32\ZoneLabs\avsys\instdrivers\x32 andC:\WINDOWS\system32\ZoneLabs\avsys\instdrivers\w2kxp32
kaspersky lap
It showed up on my computer after someone had opened one of those links sent on msn,When i type the letter 'k,l,or 1" all threee pop up at the same time, or typing other letters random ones will show up..
After installing the free version of zone alarm on my XP machine it would not boot. I could not even boot into Safe Mode. Safe mode stopped after executing KL1.sys so I used Linux to go in and renamed the file with the extension .bak and Windows would boot again.

Rating chart

Summary: Average user rating of kl1.sys: based on 13 votes with 11 user comments. 9 users think kl1.sys is essential for Windows or an installed application. One user thinks it's probably harmless. One user suspects danger. 2 users think kl1.sys is dangerous and recommend removing it.

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Best practices for resolving kl1 issues

A clean and tidy computer is the key requirement for avoiding problems with kl1. This means running a scan for malware, cleaning your hard drive using 1cleanmgr and 2sfc /scannow, 3uninstalling programs that you no longer need, checking for Autostart programs (using 4msconfig) and enabling Windows' 5Automatic 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 6resmon 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 7DISM.exe /Online /Cleanup-image /Restorehealth command. This allows you to repair the operating system without losing data.

To help you analyze the kl1.sys process on your computer, the following programs have proven to be helpful: ASecurity 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. BMalwarebytes Anti-Malware detects and removes sleeping spyware, adware, Trojans, keyloggers, malware and trackers from your hard drive.

Other processes

kl1.sys [all]