Ensuring security of electronic hardware has recently attracted much attention. While a majority of the work in this domain has focused on integrated circuits, printed circuit boards are just as susceptible to unwanted and unauthorized modifications during their manufacturing. Prior work in this domain has shown some examples of failures that can stem from intentional and unintentional board-level modifications. In this paper, we provide an in-depth analysis of previously unexplored board-level modifications and show that a number of attack modes cannot be detected using traditional methods. We also show that it is possible to detect attack modes that are most damaging to the board operation by redesigning the board with additional accessibility and adding specialized test sequences.