The 24-year-old was a free agent after leaving Dundee at the end of last season and impressed in a couple of pre-season outings with the Bulls.
Samson started his career with Kilmarnock and had has also spent time with Dundee United and Ross County, while he has also had loan spells with St Johnstone and Queen of the South.
He will compete with Darren Randolph for a starting spot at Edgar Street, with the latter having joined on a season-long loan from Charlton Athletic.