When Karim Rattani isn’t manning the till at the local Subway franchise in his adopted hometown of Cartersville, Ga., he’s usually tinkering with code. The 21-year-old Pakistani native is the lead programmer for two very different yet complementary online services: One lets people launch powerful attacks that can knock Web sites, businesses and other targets offline for hours at a time; the other is a Web hosting service designed to help companies weather such assaults. Grimbooter Rattani helps run two different “booter” or “stresser” services – grimbooter[dot]com , and restricted-stresser[dot]info .