We need to invert this relationship between Strzok and Contreras to identify other bad actors. A FISA/Federal Judge is a far more powerful position than Strzok had. If there is a shadow network, this judge will have many other connections to it. FISA court records may be sealed and secret, but his regular federal docket is not.
The biggest question of all though is figuring out how cases get assigned to him. If you want to compromise the courts, you either need to compromise ever Judge(unlikely given life tenure) within a District or have control over how cases are assigned. Does anyone have an understanding of how cases get assigned to particular federal judges among the pool of possible candidates? This function is the key to controlling the court system.