Three types of rogue threats that we see on a regular basis are Internet of things devices such as the Philips Hue light bulbs which have been shown to be exploitable from outside of buildings wireless routers that people plug into the network which is outside of your control. Rogue apps or personal programs that people are using which are not approved by the organisation could be pirated and may not be backed up which could result in losing data through either intellectual property leakage, or through simply being lost when that person takes that with them.
Businesses need to set a tight policy that insists that all applications network devices and other IT related cat is passed through the team to make sure that it is properly implemented.