Attack starts with a phishing email
https://www.bleepingcomputer.com/news/security/trickbot-teams-up-with-shatak-phishers-for-conti-ransomware-attacks/
A threat actor tracked as Shatak (TA551) recently partnered with the ITG23 gang (aka TrickBot and Wizard Spider) to deploy Conti ransomware on targeted systems.
The Shatak operation partners with other malware developers to create phishing campaigns that download and infect victims with malware.