What is Teefer?

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

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

Teefer.sys file information

The process known as Teefer Driver belongs to software Sygate Personal Firewall or Sygate Personal Firewall Pro or Sygate Teefer Driver by Sygate Technologies (

Description: Teefer.sys is not essential for the Windows OS and causes relatively few problems. Teefer.sys is located in the C:\Windows\System32\drivers folder. Known file sizes on Windows 10/8/7/XP are 60,496 bytes (54% of all occurrences), 55,891 bytes, 61,008 bytes or 85,456 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 service has no detailed description. Teefer.sys is not a Windows system file. The program can be removed using the Control Panel's Add\Remove programs applet. Teefer.sys appears to be a compressed file. Therefore the technical security rating is 25% dangerous, however you should also read the user reviews.

Uninstalling this variant: If you run into problems with Teefer.sys, you can uninstall the program using the Control Panel ⇒ Uninstall a ProgramSygate Personal Firewall or Sygate Personal Firewall Pro.

Recommended: Identify Teefer.sys related errors

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

installed by Sygate Personal Firewall on XP systems
  Alan R   (further information)
Gave me a bluescreen
It is indeed installed as part of Sygate Personal Firewall. There are two copies on my system: teefer.sys in C:\Program Files\Sygate\SPF; and Teefer.sys (notice the capital) in C:\Windows\System32. One of them gave me a BSoD for trying to write to protected memory.
  Tom H.  
On my system Teefer.sys was installed with my Ontrack System Suite 5.0 software, aka VCom.
Sygate Personal Firewall
Teefer Driver of Sygate Firewall for WinXP, 2000
I know that this file is installed by Sygate Personal Firewall on XP, but I´m getting some Blue Screens with this file as an error cause.
removed sygate firewall and it won't allow me to reboot or re-setup. Not happy.
  Donna S  
Got a Bluescreen (Stop: 0x0000007e) from teefer.sys ...
Teefer.sys is installed by sygate. it creates problem after installing the Sql Server in 2003 server envirment
My problem is with TEEFER.vxd. It stops Win 98SE loading and says I must run Win setup to clear it but every time the setup reboots I get the same error msg.Can start in safe mode but have not attempted any fixes yet. I do have Sygate firewall installed tho....
sygate driver
It causes BSOD's
Installed and used by Sygate personal firewall, said to sometimes cause unknown errors.
  The Angel Loving All Souls   (further information)
Blue Screen in Windows 2003 - argh!
  Kirby L. Wallace  
Teefer.sys in XP Pro allowed downloading of SP2 but blocked the installatiion and in 98se blocked the re
It may be spyware or adware that`s named (camouflaged) like this, even if it`s originally from sygate. I never installed Sygate software in my computer, and I had never heard of it, yet I still had it in my system. (???)
  Tony   (further information)
Appears to be associated with with Sygate Personal Firewall. I uninstalled SPF with Add/Remove software & computer is working good now.
  Mike R  
i just removed the teefer.sys file from : C:\Program Files\Sygate and all is fine again now
kills win2000, deadended to memory dump, after upgrading system suite6 win98 unable to load it, but keeps working
necessary sygate file
Also part of Bullguard AntiVirus
  Bart M   (further information)
May be needed for SPF to run, but the bloody thing causes BSOD in Windows XP when Internet Connection Sharing is enabled...
The mother of sygate & Co do in the CIORA
associated with System Suite/Windows 98
Definitely associated with Sygate Personal Firewall
  Tim G  
In my case I was getting the bsod until I updated a D-link driver, and don't appear to have a problem with it now. It seemed to conflict with the old driver, which also caused bsod with a file called a5agu.sys.
  Jack R.  
Installed because of sygate personal firewall
Got 2 blue screens so far, by trying to write to read-only mem. I know that is from Sygate Personal Firewall but I´ve been using it for a while and only recently got this problem
It looks like Symantec is using Teefer in their PreRelease Evaluation of their Endpoint Protection software. I was not aware that it had installed, and I don't seem to be having issues with it, I was just surprised when I looked at my network settings and saw an unknown service (listed as Teefer2 Driver) installed.
  Shawn Nestingen  
a sygate firewall file
Sygate Firewall Teefer Driver. Causes BSoD when used with (AMD Processor Driver AMD Dual Core Optimizer Throttle\PerfIdlePackages=1 boot.ini /usepmtimer key -- don't know which of them)
its a network driver for sygate and other apps
Sygate Personal Firewall, but can get infected like any file
  IT   (further information)
all I know is I have sygate personal firewall and like everyone else here I also have a teefer in my pc so it must be legit. always last driver to load in my desktop
  no game mike  
Teefer.sys is also with System Suite 4.0 as well. I have been using this for several years without any issues on XP Pro. The BSOD just happened on both my systems, Main and Backup when I installed sotware updated. So far I have traced it to crl. godaddy and verisign verifications links for vendor software verification. The vendor is responsible for what the process does during this verification and what is saved on your system. The BSOD only just happened within the last month so I am still investivating it. Will add more later.
AVG Antivirus Free edition 2012 reports this as a root kit - my guess is they want to break your system and force you to buy more of their tools
Since its related to Sygate and is common on sygate install Im assuming it is the firewalls 'hiding' itself from intruders. Anti virus sees that hiding activity as suspicious. For instance windows always says I have no firewall when Sygate is running. My guess Sygate doing its job.
Teefer2 hijacks network controller essentially disabling the NIC both wired and wireless. Could not stop service or disable port. Needed to format drive and reload OS to remove.
  Larry M  

Rating chart

Summary: Average user rating of Teefer.sys: based on 41 votes with 39 user comments. 23 users think Teefer.sys is essential for Windows or an installed application. 8 users think it's probably harmless. 3 users think it's neither essential nor dangerous. 5 users suspect danger. 2 users think Teefer.sys is dangerous and recommend removing it. 6 users don't grade Teefer.sys ("not sure about it").

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Best practices for resolving Teefer issues

A clean and tidy computer is the key requirement for avoiding problems with Teefer. 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 Teefer.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

Teefer.sys [all]