SiteLock Malware Detector probes your site to determine if fields and forms on your site are vulnerable to attempts by hackers looking to exploit these forms to gain access to your data. This will result in attempts to submit forms on your website with encoded data.
If you wish to stop receiving these e-mails or entries, you may want to do some validation on the fields within your form to ensure that data is being submitted in the correct formats before triggering e-mails or database inputs. Since SiteLock inserts data that would not likely be valid for any fields on your site, these validation measures should stop you from getting these empty e- mails or entries. It is also a good coding and security practice to make sure your website visitors are providing the correct data in the expected formats.