Sucuri Memory Limit Issues During Scan

WordPress websites that have the Sucuri Security - Auditing, Malware Scanner and Security Hardening plugin installed may experience an issue with exceeding the PHP memory limit during scans.  Most frequently this results in daily emails to the site admin email with the subject line:

[Site Name] Your Site is Experiencing a Technical Issue

These emails include information to indicate that the Sucuri plugin is the cause of the issue and also the following Error Details:

An error of type E_ERROR was caused in line 431 of the file /home/sitefolder/public_html/wp-content/plugins/sucuri-scanner/src/fileinfo.lib.php. Error message: Allowed memory size of 536870912 bytes exhausted (tried to allocate 134217736 bytes)

The issue may also cause problems with publishing functions on sites, such as adding a new post.

Solution:

Access the site via FTP or a hosting file manager and navigate to the wp-content/uploads/sucuri directory.  You should see two rather large log files named sucuri-oldfailedlogins.php and sucuri-auditqueue.php.  Deleting these two files resolves the memory limit issue.  It also clears the logs for failed logins and audit queue, so be sure those aren't needed.

This issue can return in the future as these log files get large again.

Source: WordPress.org Forum