Yes and no. You can get federal law enforcement protection (other than being shipped to Arizona with a new name) if you are a witness or other person who has been threatened in conjunction with a federal investigation, but this is not the Secret Service's jurisdiction. Secret Service only protects the Pres and Veep and their families and candidates for these jobs along with high ranking federal officials in certain circumstances (credible threats against the Supremes would get them Secret Service protection). The Secret Service also fights counterfeiting, which is why they are part of the Treasury Department, but that's just a bit of random trivia. Otherwise, the relevant investigating agency will provide the protection. If the situation is fuzzy and it isn't clear who should be doing the protecting, the FBI will generally do it.
