Aside from using browser headers, I want to blacklist/whitelist browser and plugins from my site so that I can prevent these older unpatched systems from (1) being a general user of my site (2) removing those 'targets' from would-be-attackers reach.
My goal is to define some kind of endpoint security standard for users who access my site, but without directly managing the environment, as they are customers.
Is there a standard way to use Whitelisting or Blacklisting to control browser access to my site?
For example, I want to prevent any browser that has outdated Flash, but I want to permit them if they have no Flash at all.
You could use modernizr.com to detect the browser and features?