Everything

One of the most obvious applications of elemental mastery in the modern world involves blacking out electrical systems. For small areas, this simply requires a few successes with Forces 2. Larger systems and power-grids demand more successes and higher Ranks; blacking out a city, for example, would demand Forces 5 and a fair number of successes, not only because of the vast scope of the blackout but also because the mage has to overcome the many levels of redundancies built into any major power-grid.

Unless the mage is in close proximity of the generators for the system in question, a blackout may also demand Correspondence (to reach to the heart of the system), Matter (to demolish essential machines), or both. Yes, the Data Sphere works just as well as normal Correspondence when you’re trying to crash a system. For details about overcoming networks and security measures, see the Computer Systems optional rules