Simply.com uses an advanced filtering system (Web Application Firewall) to prevent and block attacks, abuses and exploitation of vulnerabilities in our customers' websites.
If this filter picks up what it thinks is an attempt to abuse your site, it will display a 555 error and disconnect for that particular visitor. This can be e.g too many failed login attempts, unauthorized HTTP queries, or IP address visits known for attack and spam.
Known 3-party services like Googlebot, Jetpack, Paypal, Facebook, ManageWP etc. are whitelisted in our security filter.
Article from the support category: PHP
