1. A method for selecting candidate prefix hijack monitors, the method comprising: assigning each of the candidate prefix hijack monitors to a respective cluster of a plurality of clusters, each of the candidate prefix hijack monitors associated with an autonomous system (AS) that indicates an AS path of autonomous systems (ASes) from the AS to a destination prefix associated with a destination AS; iteratively merging a pair of clusters with a highest similarity score amongst cluster pairs of the plurality of clusters into a single cluster until a processed number of clusters is less than or equal to a predetermined number of clusters; ranking each candidate prefix hijack monitor of each of the processed number of clusters according to a route type from an AS associated with the candidate prefix hijack monitor and an AS distance from the AS associated with the candidate prefix hijack monitor to the destination AS; and determining a highest ranked candidate prefix hijack monitor of each of the processed number of clusters.