  This paper revisits the Interaction Abstract Machine (IAM), a machine based
on Girard's Geometry of Interaction, introduced by Mackie and Danos & Regnier.
It is an unusual machine, not relying on environments, presented on linear
logic proof nets, and whose soundness proof is convoluted and passes through
various other formalisms. Here we provide a new direct proof of its
correctness, based on a variant of Sands's improvements, a natural notion of
bisimulation. Moreover, our proof is carried out on a new presentation of the
IAM, defined as a machine acting directly on $\lambda$-terms, rather than on
linear logic proof nets.
