Roles are always advertised. There are no "hidden roles" where a referral can get you in.
Don't waste your time. But if you really wanted to, be prepared for competition. Know the technology inside and out before being interviewed. Aim to pass the assessment center and keep other opportunities open whilst your in the interview process. Notify all employers, educational establishments for a reference and transcripts in advance and two personal references that are top notch. It can take months to join.