Respectfully ...
It does not fall under the scope of service mandated by Congress for the Secret Service. The Secret Service just can't jump into an investigation. They are responsible for our banking system, money cyber security and protecting the protectees mandated by Congress.
No, the Secret Service could not randomly review his computer, unless within their scope of service. The FBI could and it does fall under the FBI as the federal investigative agency.
I'm very familiar with government and the powers of each department. Have hosted, planned, executed numerous events with the Secret Service and Congressional protectees.
I'm also very aware of government contractors. This man did not work for the White House and no one has been able to produce any documentation showing that he did.
My opinion, either the media misspoke as to the agency or there's more to the story and I'm betting it's related to money.
Moo...