High Noon

Published independently and later collected in Security Breach.
"Nora Brooks and Randall Goodwin face their toughest assignment yet as they follow a cyber terrorist into the canyons of Zion National Park. A dozen EMP attacks have been planned to occur on the same day at the same time—high noon. Nora Brooks is going to need all the technical expertise her partner possesses, as well as the rappelling skills of National Park Ranger, Tom Anderson. Together the three might be able to stop the attack in Zion, but even if they do there's no guarantee that the other eleven attacks won't proceed as planned."