Filtering technologies are divided into two types: Pass-through (sever plug-in based) and Pass-by (standalone-based).

A Pass-by filter usually monitors and filters network traffic with the help of port mirroring while a Pass-through filter monitors and filters network traffic on a gateway or bridge.

The differences between Pass-by filtering and Pass-through filtering: Advantages of Pass-by filtering:

1. Pass-by filtering is easier to be deployed. You only need to setup a mirroring port in your switch without the need to change your network topology. However, since pass-through filtering needs to be installed in the gateway or bridge, usually you need to change your network topology to deploy a pass-through filtering product.

2. Pass-by filtering product, such as WFilter Enterprise, only deals with copies of network packets, without any delay of the original packets. Even a pass-by filtering product stops working, your internet connection stays alive.

However, because a Pass-through product “stops and checks” network packets, it is unavoidable to make slight delay to your internet access. And, when a pass-through filtering product stops working, you will lose your internet connection.

Disadvantages of Pass-by filtering:

1. Port mirroring is required for pass-by filtering, you can not monitor or filter your network without a manageable switch.

2. A pass-by filtering product sends RST packets to terminate TCP connections, however, UDP traffic can not be blocked by pass-by filtering. Usually, you also need to block certain UDP ports in your router for completely blocking.

3. Traffic shaping and QoS is unavailable in pass-by filtering, since it only deals with copies of network packets.

For more information about WFilter technical details, please check: WFilter Inside Technologies.