Wiktionary
intraterrestrial
a. (context microbiology English) Living deep underground. n. 1 (context microbiology English) a (l/en: microbe) which lives deep underground 2 (context ufology English) any of a race of (l/en: sapient) beings who live inside the (l/en: Earth) and operate (l/en UFO UFOs)
Usage examples of "intraterrestrial".
Zealot droned on within me, identifying coincidences as correlations, arguing that common elements in extra and intraterrestrial religions proved the universality of his Faith.
So, yes, we communicate with intraterrestrials and extraterrestrials, the latter being too far away to offer us much and we have yet to decipher much of their language.
There's never been any documented evidence that the intraterrestrials have harmed anyone.