The U.S. Secret Service has a long and storied history of safeguarding America’s financial and payment systems from criminal exploitation. The agency was created in 1865 to combat the rise of counterfeit currency following the Civil War. As the U.S. financial system has evolved - from paper currency to plastic credit cards to, now, digital information - so too have our investigative responsibilities.
Today, Secret Service agents, professionals, and specialists work in field offices around the world to fight the 21st century’s financial crimes, which are increasingly conducted through cyberspace. These investigations continue to address counterfeit, which still undermines confidence in the U.S. dollar, but it is credit card fraud, wire and bank fraud, computer network breaches, ransomware, and other cyber-enabled financial crimes, that have become the focus of much of the Secret Service investigative work.
https://www.secretservice.gov/investigations
The threat of counterfeit U.S. currency to the financial system of the United States continues to evolve. Advances in technology, the availability of scanning and printing devices and the adoption of the U.S. dollar by nations as their legal tender have exacerbated the global threat.
https://www.secretservice.gov/investigations/counterfeit
The Secret Service has since its creation after the Civil War been the agency that investigates counterfeit currency. It was an agency of the Treasury Department until 2003 when it was transferred to DHS.