The selection process is pretty technical and exhaustive in nature. There could be a written test as well depending on the vertical that you have applied for. Please note that the interviewer can ask you to solve some case studies too, thus be prepared for that too.

I heard that Nielsen had vacancies through an ex-colleague in a previous organization. I emailed my resume with a cover letter to the id given by my contact. Within a week, an HR person contacted me to fix up a telephonic interview. This was a general personal interview. A fortnight after this, the HR manager called to say that a domain expert from the region will be calling me for a technical interview. Over the next fortnight, my technical interview was done and I recd an email with an offer letter.