Gmail has included a number of modified SPAM messages in the "Sent" directory to appear created by the user account owners themselves.
Even if it does not offer advanced facilities for managing unwanted messages, Gmail is generally rated for the anti-SPAM filter quite efficiently. But a group of spammers found a way to fool detection filters, giving the impression that they are sent by the same user.
As a consequence, Gmail moved the incoming messages directly to the "Sent" section, confusing the users who suspected the compromise of email accounts first, surpassing the two-step authentication system and the set password.
Fortunately, with the exception of unusual propagation, messages sent to a small group of Canadian users do not differ much from the SPAM that is usually blocked by Gmail filters
Currently, Google is working with the owners of the servers on which the SPAM attack, a Canadian telecom company, was initiated, and Gmail filters will be updated to block such messages in the future