Yes, I would say a demon could manipulate a computer. When a demon takes control of a person, it is called “possession.” When a demon takes control of a house or object, it is called “infestation.”
In an
Ignatius Insight article, Fr. Gabriele Amorth wrote:
"Diabolic infestation. Infestations affect houses,
things, or animals.“In Matt Baglio’s book The Rite, on which the movie is based and follows the formation of the exorcist Fr. Gary Thomas, it reads on page 47:* Infestation is the presence of demonic activity in a location or object, such as a 'haunted house.”
The various kinds of phenomena that can occur in this situation are vast and include…
interruption of electric current or malfunction of electronic devices*…Baglio’s sources are many throughout the book. My
review can be read here.
Anyway, I don’t see why a computer would be off-limits to the devil since it has a certain power over this terrestrial world until the Second Coming.