Hi @hazechan916,
WP-SpamShield would not cause high CPU usage like that. What could cause high CPU usage is errors in PHP or something that is misconfigured, which will require some debugging on your site. We put a lot of work into making sure that the plugin is extremely light on resources. We also monitor CPU usage very closely to ensure it would never cause an issue like that.
Please see FAQ which explains this in more detail:
FAQ 15: Q: Will WP-SpamShield slow down my site, and is there anything I can do to optimize my site for it?
Also, please take note of the sticky post at the top of the forum — PLEASE READ BEFORE POSTING — Updated June 2017, and follow the links there to our support documentation and to our official support page. (These links are also in the plugin’s settings page.)
Please note that we don’t provide support here at the forums, but we do provide excellent support through our site, which is better equipped to help our plugin users.
Please direct all support requests to the plugin’s official support URL, the WP-SpamShield Technical Support page.
– Scott