"Unfortunately, many times, such messages happen beyond registered telemarketers. Consumers can complain on DND (do not disturb) 2.0 and we will be able to stop them immediately. However, individuals continue to receive stock tip messages even after registering for DND service.In bulk SMS, sender identity is captured in short codes. For instance, in the code AM-XYZ, AM stands of Airtel Mumbai while XYZ is the brokerage or bank. "What attackers would mostly do is register a short code that reads very similar to a broker or a bank's actual short code.

Source: Economic Times January 21, 2018 17:34 UTC