What is a Troll Army?

The web brigades (Russian: Веб-бригады), also known in English media as the troll army, are state-sponsored Internet sockpuppetry groups linked to the Federal Security Service of the Russian Federation.They are suspected to be organized teams and groups of commentators that participate in Russian and international political blogs and Internet forums using sockpuppets and large-scale orchestrated trolling and disinformation campaigns to promote pro-Putin and pro-Russian propaganda. It has also been found that Wikipedia articles were targeted by Russian internet propaganda activities.

reference: https://en.wikipedia.org/wiki/Web_brigades