A friend of mine asked me to set a security system for his 2nd house. I am thinking of connecting some motion detectors and vibration sensors to an esp32 which will be connected to a cloud IOT platform via the ISP router. I heard that burglars can use some "wifi jamming" technics to blur the wifi signal of their victim. Hence, the esp32 will fail to connect to the ISP router/IOT platform.
I would like to add that some sensors will be wired directed to the ESP32 and some will be connected to an Attiny85 that uses an nrf24l01 module to send the data to the ESP32.
My questions are:
1- is there any way to reliably detect the wifi attack, blurring,jamming...etc?
2- Is there any way to fight against the wifi attack in the esp32 side?
3- Any similar experience sharing is highly appreciated.
Thank you.
Perhaps hardwire your connection??
All I know is that a closed circuit would be harder to penetrate.
In general, yes, but "reliably"? That is not an attribute of WiFi. 
Losing connection over WiFi would be a strong indicator of jamming - whether intentional or not.
Well, no! 
It is as the name says, "wireless". The frequency band used by WiFi/ NRF24L01 - 2400 MHz - is shared by many services (it is an "ISM" band). Whatever system is used - even the "spread spectrum" used by WiFi - expects to operate with a strict protocol and is easily susceptible to a suitably configured jamming signal.
WiFI is never appropriate for a "mission critical" or business application.
I agree. A wired circuit is more secure. However, I will be using an esp32 that doesn't have a wired connection.
Thanks. Will bluetooth be more secure? I can use wifi and when I detect that connection is lost I switch to bluetooth (???).
So on what frequency do you think bluetooth operates? 
2.4 GHz. I see what you mean.