Hewlett-Packard's Zero Day Initiative (ZDI) yesterday spelled out the rules for its March hacking contest, Pwn2Own, which will put two-thirds of $1 million in prize money on the table for researchers who can hack the biggest browsers and most popular plug-ins. ZDI is HP's bug-bounty program, run by its TippingPoint division, a maker of intrusion prevention system (IPS) and firewall appliances for corporate networks.