How does Blockd work?

Block-d uses a grep function - namely ngrep or "network grep" - which looks for a target expression on the network, within the transmission, and if it finds the expression, the data stream is reset with a kill command. Essentially the script blocks the traffic which contains the target expression(s) and thereby prevents any data transfer of this kind.

The script is so effective that while blocking sites like e.g. Facebook, the site's gadgets, toolbars, like buttons and other web applications do not load at all.