Nineteen-year-old Dutch left-back van Aanholt has joined the club on a month's loan deal with Jose Enrique facing several weeks on the sidelines with a hamstring injury.
Hall, 29, has arrived from QPR until the end of the season with Steven Taylor facing months out with medial ligament damage.
On Moses, Toon boss Chris Hughton said: "It's been documented that we are very interested in signing the lad.
"Most people are also aware of the circumstances with Crystal Palace and the situation they are in, and we hope to make progress on that over the next couple of days.
"It's one we have a very, very keen interest in.
"He is a player who has an ability to score goals. There is a power and pace, but it is his potential.
"Around what we are trying to do here this season, which is the most important thing, there also has to be an eye on the future, and he is certainly a player of wonderful potential."