Consider this. Most hostile satellites would have comm gear and sensors pointed down towards earth. Approach from the high side, attach small device to solar panels, leave. Later on, device deploys, slowly covering an ever increasing portion of the panel. Available power drops, looks like failure in the panel, mission kill on the bird.... Or maybe it needed to change orbits up there looking for global warming. ...
Can’t ground trackers watch where this is? I know it’s small, but I’ve watched satellites go overhead. Isn’t hard to hide? Clearly, not much anyone could do but watch. Until you blow the sat its chasing.