Hiding in the Solar System.

This is obviously of only theoretical personal interest:

Assume a perfectly malevolent, social and very scientifically advanced carnal
species coexisting with us in the Solar system, but whose intent is to always
stay absolutely hidden from human sight, 24/24, 365/365 and as close as possible
to us. Let's assume that this assumption (staying hidden from human sight and as
close to us) serves some unknown purpose of its evilness against humans.
Something like the Predators, for example.

"social" means in order to survive as species it needs some sort of colony
(which obviously generates some "noise" as a byproduct of its existence), like
we do.

"very scientifically advanced" means advanced enough from our standpoint, but no
nonsense science, like cloaking Romulan/Klingon devices or Predator
"light-bending" thingies.

"carnal species" means the corresponding life form is of similar makeup to us,
subject to gravity, death, aging, etc.

"Human sight" means any observation means, such as radio and optical equipment,
spectrographs and in general any scientific device we use today.

I would be interested in knowing your opinions about optimal locations where
this species could be located.

The allowed range is the entire solar system (Sedna, Eris?), so please take
careful account of the dynamics of the entire system before answering. Locations
which eventually turn and face Earth are not acceptable, as they are surveyable
by human instruments.

In a sense this is a two-objective optimization problem, for objectives:
"Hidden" and "Close".

Many thanks in advance,
--
I.N. Galidakis