Top 20 NuGet anti Packages

Cleans HTML from constructs that can be used for cross site scripting (XSS)
Google ReCaptcha wrapper class for quick and easy validation (injectable service for ASP.NET Core apps).
ClearSale anti fraud platform client API.
Rule based HTML sanitizer using a white list. Documentation at:
ProceXSS is a Asp.NET Http module for preventing xss attacks.
You can do a lot of http requests through different proxies.
A package to secure all controllers actions in your application by default by disallowing anonymous access, and requiring each HttpPost action to be passed an anti-forgery token. Anonymous access to a controller action needs to be explicitly set by use of an attribute.