Clots can block the flow of blood to the heart or brain and cause a heart attack or stroke.

VOA: special.2009.10.20

Once security companies were able to identify the control servers for the attack, they could identify and block the attack, and the zombies went quiet.

FORBES: Social Media Brings a New Wave of Threats, Part 2

After the attack on the World Trade Center, a block from AmEx headquarters, the plan was scrapped.

FORBES: Monarch on a Mission

The messages suggest that the attack was organised to protest against efforts to block access to The Pirate Bay's (TPB) file-sharing pages.

BBC: Virgin Media attacked by opponents of The Pirate Bay block