"Few years ago, BSNL was regarded as a biggest spammer in the country, and with a robust Cybersecurity mechanism in place, we are not even among top 20 spammers list today, Shrivastava added."
Quite sure , its because spammers on BSNL network realised that this is a crappy network and moved on to better network , i doubt it was because of the actions taken by BSNL , if you are going to spend 100 crore on security , and then your decision is blocking ssh port, may be you are just doing it wrong