https://www.theguardian.com/world/2020/apr/11/singapore-bans-teachers-using-zoom-after-hackers-post-obscene-images-on-screens

‘Very serious incidents’ have forced suspension from online schools as conferencing app faces renewed questions over security

Singapore has suspended the use of video-conferencing tool Zoom by teachers after “very serious incidents” in the first week of a coronavirus lockdown that has seen schools move to home-based learning.