Here is an Excerpt from FAA Advisory Circular AC 120-76B regarding EFB's:

"(2) The operator should identify a means to demonstrate that adequate security measures are in place to prevent malicious introduction of unauthorized modifications to the EFB’s operating system, its specific hosted applications, and any of the databases or data links used to enable its hosted applications (i.e., security risk assessment). The operator also needs to protect the EFB from possible contamination from external viruses."

The above is a recommendation only, but it explains why many air carriers ISSUE an IPAD (EFB) to crewmembers and "lock it down" so personal Apps won't be downloaded. This helps prevent possible "interfere" with displaying information that is essential for Safety of Flight...