In general, Zoom’s problems fall into three broad buckets: (1) bad privacy practices, (2) bad security practices, and (3) bad user configurations.
Privacy first: Zoom spies on its users for personal profit. It seems to have cleaned this up somewhat since everyone started paying attention, but it still does it.
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Now security: Zoom’s security is at best sloppy, and malicious at worst. Motherboard reported that Zoom’s iPhone app was sending user data to Facebook, even if the user didn’t have a Facebook account.
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Finally, bad user configuration. Zoom has a lot of options. The defaults aren’t great, and if you don’t configure your meetings right you’re leaving yourself open to all sort of mischief.
https://www.schneier.com/blog/archives/2020/04/security_and_pr_1.html