How is spam sent on Telegram?

Question

Fight against spam

Registered a new account in Telegram, from the desktop. I didn’t launch Telegram on the phone, I just received the code via SMS (the phone is a stupid dialer). About 5 minutes later, spam came in from one of my phone contacts - animated gifs.
How does this happen? Does he have some kind of virus in his phone that monitors the appearance of new contacts in Telegram? (Knowing this person, he obviously does not send it himself.)

Answer 1

Telegram has notified all users who have your number about your happy appearance.