DDoS-Guard is a Russian Internet infrastructure company which provides DDoS protection, content delivery network services, and web hosting services.
Google AdSense is a program run by Google through which website publishers serve advertisements that are targeted to the site content and audience.
HTTP Strict Transport Security (HSTS) informs browsers that the site should only be accessed using HTTPS.
PHP is a general-purpose scripting language used for web development.
VK is a Russian online social media and social networking service.