Your Bitwarden vault is protected by your master password, salt (email address), and iterations. That is then sent to the server where it’s given a random salt and 200k more iterations before being stored for login purposes.
It’s hard to defend against malware, it’s like trying to protect your home from a burglar when the burglar is already in your home. The best advice is to keep your computer up to date and run anti-virus software.
Life is not like the movies, don’t let your paranoia get the best of you.