Hi Maria Elena,
We use and recommend Akismet. It’s by far the best plugin for blocking and managing comment spam. Plus, since it’s created by Automattic, it has the best support team.
Akismet has blocked 63,703 spam comments on this site, and we’ve never had a legit comment flagged as spam. From time to time, a comment or two may sneak past their filter, but for the most part, it’s been rock solid.
Hope this helps!