I've trained myself to be sensitive to different types of energies (or whatever they really are). But my spells are to manipulate these energies in ways I wish teem to be.
For example, I felt 'malice' from a server I and a colleague were working on. Servers shoukdnt have emotion, unless someone left that imprint. Well, turns out it was a popped machine from 6 months ago from an Apache Tomcat install where they badly fixed the hacked server. And they didn't clean it well enough. Rkhunter and chkrootkit both found kmods that were still resident.
In that case, it was noting more than feeling maliciousness, and then using my technical prowess to prove it.
Other cases, I've done things like debug heisenbugs simply by willing them to resolve or make the error evident. Most of those types of "spells" are mental. I dont need candles or whatever.
Another time, someone in our hackerspace got ahold of Mathers Grand Key of the Legemetton and decided to do a demonic summoning as provided. He was an atheist, and was just following the motions. It worked. He trapped something there, that was frightening every sensitive type that walked through the doorway.. I found it, and took care of it in the proscribed manner (release, dismissal, and freed from any cost it may have incurred to me).
But to answer your question, no its not like casting D&D fireball. Most things dont have physically perceivable effects. But the underlying question: yes, harm to others can very much be done.