Battle of the Immortal — Jeff Norton

Hordes of Uploaded (the online incarnations of dead people) have escaped the Metasphere and taken over the bodies of living people in the real world. As warring factions vie for control of the online sphere, computer viruses and rocket technology are among the weapons used in a savage battle between the living and the dead. Jonah faces an ever more complicated future - and must make a terrible choice about his own Uploaded father...