It's been discussed for decades:

For example,
http://www.jamesoberg.com/1984terraandseti_ter.html

Alternately, the stars themselves would be engineered to promote stability and
inhibit dangerous radiation outbursts. At least by this point, such engineering
activities could become apparent across galactic distances. Whether these
manipulations would be recognizable as artificial is a serious question for
astrophysicists! And this is the key issue for SETI.

The 'signature' of ET terraforming activities and stellar engineering
activities is a worthy topic for speculation. From one direction, currently
conceivable activities for future terrestrial civilizations can be extrapolated until
the applied energies become detectable at galactic distances, and those signals
(an accidental by-product of activities with other intentions) predicted. From the
other direction, observations already made can be compared against
hypothesized artificial causes, such as the 'Little Green Men' suggestion for
pulsars, or the only-half-whimsical suggestion that Seyfert galaxies are alien
mega-Chernobyls. This last suggestion raises the serious observation that once
such energies are harnessed for artificial purposes. they may not always work:
recognizable ET signatures may consist of news that some civilization's greatest
engineering effort has failed spectacularly. Or even more sadly, the traces may
reflect energies released in an unimaginable technological conflict (what we
today would call a 'war') between striving forces whose technical cleverness far
outstripped their wisdom. Extrapolating from our limited sample size, that is not
an inconceivable outgrowth of technological activities.