*YES*.

Correspondence is cool, but 

* any "remote" modification of living beings requires Life (and materials - Matter),
* exemplary Sphere Effects indicate so: `whereami?` requires Spirit level 1 to guess in which Astral Domain you are or Mind to realize it's a dream/hallucination; `window` requires Time or Spirit to watch different eras / worlds.
* Umbra = Spirit. Digital Web = Umbra. Therefore **Digital Web = Spirit**.

I've written this mostly from memory, but I doubt revised changed this.

Of course, if your GM says you can, you can... but **so can everybody else**. And that makes Spirit kinda irrelevant Sphere.