Robert Rodriguez, field officer with the US Secret Service's Electronic Crimes Task Force, said the unit had gradually built up trust with big businesses by deliberately keeping its work out of the limelight.
Speaking at the RSA Conference in San Francisco, Rodriguez said the Task Force realised from day one it was more important to respect the confidentiality of business, than to seek publicity for the unit's successes.
"Our priority is not to position the task force as an agency that is taking credit for investigations. That's one of the principal reasons why industry is working with us and trusting us," he said.
The unit, one of nine across the US, works closely with experts from industry and academia in California to track and investigate computer crime.
Rodriguez said businesses deliberately tested the unit by filing small test cases to discover how the unit would react, gradually building up a level of trust.
"We started out by building relationships and we developed that trust over the months with large companies in the San Francisco Bay area. We started out with half a million-dollar cases; now we are up to $20m," he said.