Google Calendar has been hacked, how to find the reason (entry point)?

Question

Google

Hello!
Faced a strange problem.
My account uses a strong password (33 characters) and also uses Google Authenticator.
Google account is used for oAuth on other sites and in android applications. I didn’t notice anything like this before, but literally 2 days, as I noticed SPAM events in Google Calendar.
Removed all unnecessary access to applications and sites. I left only those that I trust. Removed SPAM activities.
One suspicion - I use linux mint and the problem appeared after adding a google account to the Calendar application on linux. True, scanning in clamav did not give any results.
Who faced it? And what was the problem? Nothing else has been hacked, only google calendar.

Answer 1

You weren't hacked, it's an old way of spam :) It got out a month ago.
The principle is very simple, your mail is recognized and an event is created with a "good" broken account where you are invited. Therefore, if you go into the message itself, then there will be a button Yes / No, I will go / I will not go. If you do not answer, then you will have to delete one by one. If you answer No to all, then you will be able to delete them in bulk.
To protect yourself:
Settings -> Automatically add invitations -> No
Disable Automatically add events from Gmail to my calendar