There are two major theories of what the Habiru actually were, –and the most popular one is found elsewhere in this series of articles. Explaining that the Habiru were actually the very first of the Hebrews. However, given a substantial amount of evidence, it is more likely that there were Habiru, that were the Hebrews, but then there were also the more loosely formed bands of criminals that were also called Habiru. The theory that all the Habiru groups were actually the first of the Hebrews is putting things too simply, for a few different reasons, the least of which not being human nature, which has been and will be present until the very end.
During those long ago ages, cities and kingdoms, various societies, had runaways, criminals, thieves, of all different language, cultures, and ethnicity, that either ran away, escaped justice, or were exiled from their home cities. The men would form into groups of nomadic criminals, and made enemies easily, because usually for every city they visited, there was also a man among them who was not welcome there. That stigma stays with a group, and makes honestly living impossible. So turning to a life of crime is easy enough, thus became the Habiru, invaders and barbarians who sacked towns they came to.
However, there also other nomadic tribes in the Fertile Crescent, and some of multi-ethnic culture, and perhaps some not. It seems likely that their were many groups of nomads who were killed because of their supposed resemblance to Habiru. Also, group of different ethnicity, and cultures could also be called Habiru, despite taking an obvious lack of interest in warring with nearby cities. It seems just as likely that there were loose groups of multi-ethnic outsiders, and exiled citizens that maintained the most honest life they could.