Homeland Security Investigations ran the sweep, called Operation Signal Break, from June 22 to July 10. A single SIM box can hold hundreds or thousands of SIM cards and route calls and messages over the internet, hiding where the traffic actually originates. Where Did Operation Signal Break Focus? What Has HSI Seized in Its SIM Box Investigations? Analysts at HSI Los Angeles will analyze seized SIM data and network artifacts in collaboration with the Counter Threat Finance Unit and the Cross Border Financial Crimes Center.