Nothing at all to do with da Vinci, I understand that the new anti-spam measures on the site are rather obscure. Thus, it is hoped that these few paragraphs might serve to explain.
When members try to log in, and insert their user name and password they will see something like this:
In this example the digits 34867 should be inserted in the box and log in clicked.
I understand that this might seem onerous but previous, simpler, anti-spam measures were less effective, resulting in the receipt of a large volume of spam mail.