Discouraged

From what I’ve read (and perhaps even experienced, though I’m not sure), negative spirits are quite real. Most often than not they are best defined by the word “misguided” – imagine a distortion in the emotions, thoughts or intent that grows ever greater. Pranotherapist Barbara Brennan describes quite clearly an encounter with a “dark spirit” in her book Core Light Healing, as well as the techniques used to heal him.
However, there also is a different type of negative spirits – those are simply beyond help, relentless in their task to harm humanity in order to further their plans, and the only solution is to either destroy them (as research shows they’re so inherently weak that the human energy is too strong for them, and they just “pop” or dissolve, perhaps in a more similar manner to a form-thought than a real being), and/or protect yourself so that you are impervious to them, at which point they will leave you alone.
Unfortunately, the fact that the available knowledge on the topic is generally so low-quality and non-specific makes things worse, because then you have little to no awareness whether or not one is involved in such a problem.
On a side note, I would also be wary of any warfare between “good” and “bad” spirits – sometimes it is just a strategy similar to the Latin saying “Divide et impera” – you split the group in apparent factions, but in the end you hold all the strings, and the objective is only that of having you side with any faction, so that you’re ultimately sided with the Puppet Master. Personally, I’ve come to trust only the “Local Cluster”, or what Robert Monroe called the “I-There”, that part of us which contains all past and present personalities – I just don’t trust any “spirit next door”, so to say, at least not a priori.