Strictly speaking nothing is blocked. Not .bin, not .com, not .scr, not even .exe. This isn’t a blacklist. It’s a whitelist. They’re simply not explicitly permitted. And I wouldn’t want to be the person, who makes a decision to permit executables.
I understand the reasoning behind it and blocking .com, .exe and .scr files makes sense. However, I don't see the need to block .bin files, is there any os that would/could execute these after downloading?
Historically? .bin and .iso may be optical disk images. Upon double-clicking where a relevant program is installed, they get mounted and
autostarted.
This isn’t my argument against permitting the extension. Just showing, how easy it is to miss such opportunities.
Having said that, putting them in a zip is a perfect solution (and kind of defeats the blocking).
The goal is to prevent unintended or unexpected execution, not to make sharing executables impossible. The latter can’t really be stopped. But the former can and it does work in this case. One can’t execute a binary in an archive by double-clicking
that archive itself under Windows.
(1) Keep in mind Windows hides the final part of a filename by default. So “circuit.png.exe” is displayed as “circuit.png” to most people.
Various security solutions may also block or blacklist the entire domain, if they detect any malicious executable or just any executable. It also prevents the use of forum attachments as “free CDN” to spread malware.
(1) To be correct, Windows for quite some time now warns if you try to run an executable. But this isn’t foolproof: people still happen to run them by accident.