4. Preparing for New Threats: Chemical, Biological, Radiological
While snipers and gunman remain significant threats, the Secret Service of 2013 is intensely focused on chemical, biological and radiological weapons and improvised explosive devices, officials say.
A technical security unit, formed in the wake of the Warren Commission, "takes a very proactive look at the security within an advance or within a visit of a president or vice president that could go wrong," Smith said.
Chemical and biological threats, like anthrax and ricin, are particularly concerning to the Secret Service because it only takes a very small amount of a substance to cause significant bodily harm, and possibly death.
5. Congress Grants Greater Powers, Responsibilities
In the 50 years since JFK's death, Congress has enacted more than 23 statutes aimed at strengthening the Secret Service and expanding its responsibilities for protecting top officials and their families.
In 1965, the Service began permanently protecting living former presidents, their spouses and young children. Three years later, protection was extended to some presidential candidates. By 1971, the mission was expanded to include visiting foreign heads of state and U.S. officials abroad on business.
White House grounds officially came under Secret Service purview in 1970, with protection of presidential and vice presidential residences expanding to out-of-state locations in 1976.
In the 1980s and '90s, Congress authorized the Service to take on new challenges of the electronic age, including investigations of credit card and computer fraud, missing and exploited children, and so-called "national special security events" that require extensive planning and coordination.