I have Ubuntu 18.04 LTS with VSFTPD. I want to deny certain users from connection via SFTP to my server. So far I have only found Q&A (here on stackexchange and on the internet in general) regarding allowing certain users to connect and denying all others, but this is not suitable for me as I have too many users with allowed access and only few users are forbidden.
My question is: How can I deny connection to specific users in VSFTPD?