Blocking Facebook and Myspace by IP address

Solution 1:

Who do you use as your DNS provider? If you can switch to someone like OpenDNS (it's free) they provide automatic (& very configurable) blocking of social networking sites, webmail, adult content etc.

EDIT: You don't have to change anything with your ISP either.

Solution 2:

On your Cisco asa you can do the following:

regex facebook1 "facebook\.com"

class-map type inspect http match-any block-url-class
  match request uri regex facebook1


policy-map type inspect http block-url-policy
  parameters
class block-url-class
  drop-connection log
policy-map global_policy
  class inspection_default
  inspect http block-url-policy

service-policy global_policy global

I would highly suggest you read the full details on Cisco's website.