Here I won't be talking about what is great about Kerio, but rather point out it's shortcomings and how to

work around them... please keep in mind that much about what I state are educated guesses. You can add "AFAIK" to the end of almost every sentence.

The major problem Kerio is BSODs (Blue Screen Of Death) from fwdrv.sys. BSODs are a form of Operating System crash, where, in this case, Windows, decides that now is a good time to crash because it didn't like something.

fwdrv.sys hooks in to the system at a low level, and given that Windows XP is really a fragile beast that's been hacked to run relatively well, any change in timing, any difference in how it works can bring about a BSOD. Thus there is a challenge of running any security software, for that matter (though many have gotten to be quite good). That said, it is hard to mix and match different types of security software, because they may conflict (an antivirus with a different brand firewall, for instance). Kerio 2.1.5 is compatible with NOD 2.7x, but not with NOD v3.x, as version 3 has become more "invasive" into the operating system, and taking on more roles than just an antivirus (it has some firewall elements). You definitely don't want to be using two firewalls at the same time.

If you are a normal user, Kerio will rarely if ever cause a BSOD (as far as I know).

Here are precautions when using Kerio:

(1) On file sharing apps, don't let max number of connections during file sharing go over 100, a nice number is 80. The following also applies if you are file sharing, whether you use a software firewall or not: if you want to be able to surf without a lot of latency, limit the bandwidth for downloading and uploading (global setting, not per share). I keep mine at 50m-bits-ps download and 20m-bits-ps (remember one Byte is 8 bits).

(2) Increase max buffer size from 4000 to 8000 (I think more is also asking for trouble)

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\fwdrv

"MaxBufferSize"=dword:00008000

The author of this article has not tried out the following:

(3) Kerio 2.1.5 is incompatible with Windows standby mode... the computer locks up (no BSOD), and you have to force-power-off and then turn your computer back on to get it going again. But there is a workaround:

1. Disable Start Firewall Automatically on Windows Startup in Kerio

Personal Firewall

2. Reboot

3. In Device Manager Click View then Show Hidden Devices

4. Under Non-Plug n Play Drivers right click on Kerio Personal

Firewall Driver and click Properties.

5. Under the Driver Tab Select Automatic under start up.

6. Reboot

7. Enable Start Firewall Automatically on Windows Startup in Kerio

Personal Firewall

8. Reboot.

Best regards,

Spacey Spade