Super User is a question and answer site for computer enthusiasts and power users. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

The IT department of our company have blocked FB. but if we keep on hitting try again button again and again after 6-7 attempts it opens. Why is this so?

share|improve this question
you could alway see the method they are using on the other side :-)… I think it might be one of the multiple IPs are finnaly reached. you could test if they use DNS block or IP block by testing some numbers… – Psycogeek Jan 20 '12 at 4:53
up vote 3 down vote accepted

Firewalls generally work on IP addresses (this is best practice). Facebook uses a content distribution network and is spread over hundreds of different servers.

It is likely that they have blocked some of the IP addresses related to facebook, but not all, and each time you try, there is a chance will resolve to one of the IP addresses that isn't blocked.

Recommend that they use a proxy server to control access to different sites, as they can more effectively block at the URL level with one.

share|improve this answer
"You are". Each time you ask your browser to open it will attempt to resolve it to an IP address. If this request goes to DNS it can come back with a different IP time, or multiple IP addresses. Try it for yourself here: – Paul Jan 20 '12 at 4:59
"Confused". Yes, you could identify an IP address that works, and use it in your c:\windows\system32\drivers\etc\hosts file. This isn't guaranteed however, as facebook pulls in content from different urls, some of which may still resolve to blocked IP addresses. So you might find some things don't load correctly. – Paul Jan 20 '12 at 5:17

They've blocked Faceless by locking out the IP address blocks used by the service. These are served out round-robin. You've managed to iterate through to a block that resolves through DNS and that isn't being blocked by the firewall.

share|improve this answer

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .