I prefer downloading OS iso files via torrent but some caution is required.
The following is a general message i.e. "you" doesn't mean 
grahamperrin .
For those that also like downloading files by torrent please be sure to validate your downloads when they complete with their 
official SHA256 or SHA512 sums.
You cannot trust the checksums from fosstorrents.com as those are 3rd party.  Sure, they've probably posted the right ones but the ONLY sums you can trust are the sums from the 
official source i.e. a FreeBSD SSL (http
s) secured URL which in this case is http
s://wiki.
freebsd.org/Torrents .  You can use the magnet links at fosstorrents.com no problem, only after you validate the download with its 
official sum will you know you have a legitimate (iso/img) file.
Security advisory summary:  Only trust the publisher's checksums sourced directly from the publisher (via a secure method, here that is SSL (https)).  (checksums being SHA256 or SHA512...)