That is one of a number of findings in security vendor that should be unsettling to enterprises that permit employees to "bring your own device," or BYOD.

The biggest mobile targets of malware so far have been devices powered by Android, since and is an open platform.

But that may change soon. Zscaler's report said in a survey covering 200 billion transactions, Apple iOS web traffic jumped from 40% in the last quarter of 2011 to 48% in the first quarter of 2012, surpassing Android, which dropped to 37%.

More iOS traffic means more Apple devices in use at enterprises, which is likely to make them more attractive to cyber criminals.