Mozilla has download mirrors around the globe. <br /> http://www.mozilla.org/mirrors.html

If you are downloading Firefox by going to www.mozilla.com then they are most certainly safe. Many of the mirrors host downloads for a variety of other opensource stuff and may be located at places like university's and such. Mozilla does not have just one or two servers for Firefox downloads as that would not be able to handle the load, especially during new releases of Firefox, more so if release in coincides with Thunderbird and SeaMonkey releases in same period. The list of primary and secondary mirrors servers for http://releases.mozilla.org is at http://www.mozilla.org/community/mirrors.html as mentioned.