I donated a server for the slacksec.org team, and the site is now coming from Rackspace. The slacksec admins have set up a mirror of the official GUS-BR packages, which is available via rsync. You can also grab the official Slackware updates mirrored here:
http://ftp.pbandjelly.org/pub/slackware.org.br/
ftp://ftp.pbandjelly.org/pub/slackware.org.br/
(links removed – no longer available)