"How small are GSM bugs?"

A. They can be as small as a Compact Flash card.

This is a question I hear frequently, along with...

"How expensive are they?" 

($20 to $80)

"Where are people getting these?" 

(ebay and on-line spy shops)

"How do they work?" 

Plug in a SIM card and hide it. Call the listening device using any phone, from anywhere in the world. Or... some models will call, or text, you whenever it hears someone in the vicinity talking!

"How do you find them?" 

In 2009, Murray Associates developed a proprietary test - Digital Surveillance Location Analysis™ (DSLA™) - which plots the location of these normally dormant devices on a computer screen map, using triangulation.