https://walltime.info/ -> Walltime is the best Brazilian Bitcoin Exchange. Serious security ( https://walltime.info/security/bug-bounty.html ), a reasonable API ( https://walltime.info/api.html ), a 24x7 operation that is also a mostly automated operation, great support and lead by technical minded people who actually understand Bitcoin ( https://bitcoin-otc.com/viewratingdetail.php?nick=walltime&sign=ANY&type=RECV ). Some highlights ( Portuguese) : https://walltime.info/blog/2018-06-20_sobre_seguranca_walltime_pt-BR.html