The secret project Developed by NSA (National Security Agency of USA) and its allies is tracing every single transmission even a single of keyboard. The allies of USA in this project are UK, Australia, New Zealand and Canada. Echelon is developed with the highest computing power of computers connected through the satellites all over the world. In this project the NSA left the wonderful method of Tempest and Carnivores behind.
Echelon is the technology for sniffing through the messages sent over a network or any transmission media, even it is wireless messages. Tempest is the technology for intercepting the electromagnetic waves over the air. It simply sniffs through the electromagnetic waves propagated from any devices, even it is from the monitor of a computer screen. Tempest can capture the signals through the walls of computer screens and keystrokes of key board even the computer is not connected to a network. Thus the traditional way of hacking has a little advantage in spying.
For the common people it is so hard to believe that their monitor can be reproduced from anywhere in one kilometer range without any transmission media in between the equipment and their computer. So we have to believe the technology enabled us to reproduce anything from a monitor of computer to the Hard Disks including the Memory (RAM) of a distant computer without any physical or visual contact. It is done with the Electromagnetic waves propagated from that device.
The main theory behind the Tempest(Transient Electromagnetic Pulse Emanation Standard.) is that any electronic or electrical devices emit Electromagnetic radiations of specific key when it is operated. For example the picture tube of computer monitor emits radiations when it is scanned up on vertical of horizontal range beyond the screen. It will not cause any harm to a human and it is very small. But it has a specific frequency range. You can reproduce that electromagnetic waves by tracing with the powerful equipments and the powerful filtering methods to correct the errors while transmission from the equipment. Actually this electromagnetic waves are not necessary for a human being because it not coming from a transmitter, but we have a receiver to trace the waves.
For the project named as Echelon the NSA is using supercomputers for sniffing through the packets and any messages send as the electromagnetic waves. They are using the advantage of Distributed computing for this. Firstly they will intercept the messages by the technology named as the Tempest and also with the Carnivore. Every packet is sniffed for spying for the USA's NSA for security reasons.