Some 400 million people change their phone's components, such as touchscreens, chargers, and battery or sensor assemblies, which are all susceptible to significant security breaches and attacks. These components, referred to as 'field replaceable units (FRUs),' communicate with the phone CPU over simple interfaces with no authentication mechanisms or error detection capabilities. Cyber security researchers have developed an innovative firewall program that adds a missing layer of security in Android cellphones and monitors for malicious code.