EVMs are not internet enabled, neither are they "programmed" by sticking a USB in them. They come in huge sealed boxes to the centres, and are carried back the same away. The data never leaves these machines. If my knowledge is correct, the data can only be accessed by a high ranking election official called the RO.
Paper ballots were the norm in India for over 40 years before EVMs were introduced. Election fraud has been non-existent since then.