Why is there a delay in blocking devices?

Our block feature makes the targeted device to believe our Fingbox is the gateway of the network. In this way, Fingbox can receive the packet and discard it. Moreover, we make the target device to believe that its IP is owned by another device. All of these low-level techniques can be bypassed by a few seconds or minutes if the router put in place some anti-spoofing or similar techniques.

To explain further, when the device tries to connect to the router, the device will be able to make the connection until the Fingbox is checking the ‘Block-list’, if the device is in the list or not. Only after checking that list, the device will be able to maintain the connection or get blocked from the network. This verification of the list might take up to few minutes and then Fingbox is able to block that device.