A field test on various mobile phone shielding devices (i.e., a tool designed to act as a Faraday cage) was conducted at Purdue University. Many shielding devices claim to radio isolate a mobile device. Unfortunately, these tools do not always successfully prevent network communication. The tests conducted at Purdue used multiple shielding devices with mobile devices operating over three of the largest U.S. providers while varying the distance from the provider’s towers.
The majority of the test cases proved that the shielding devices tested did not prevent network communication in all cases, SMS messages most often penetrated the device while shielded, followed by voice calls and MMS messages. The shielding devices may fail due to the materials not providing enough attenuation, leaks or seams in the shield, or the conductive shield acting as an antenna.
While many manufacturers claim the effectiveness of their shielding device, it is important to understand the isolation device’s effectiveness based upon attenuating signals between specific decibels. Therefore, the isolation containers tested were not 100% effective in most cases, and devices used to preserve evidence require verification.
Some of the products mentioned in the above paper have since been improved to provide a more effective radio isolation solution. Examiners should test their own products to validate that they are working properly before use.