March 20, 2017 – FBI Director James Comey indicated in a statement before the HPSCI that the investigation into Trump’s campaign was a “counterintelligence investigation”.
What is Counterintelligence and why does it matter? 
By: Lycaon @Cynacin
Counterintelligence is defined by the National Security Act of 1947 Sec. 3. [50 U.S.C. §401a] as “information gathered and activities conducted to protect against intelligence activities being conducted on behalf of a foreign government.” 
The Counterintelligence Enhancement Act of 2002 established the National Counterintelligence Executive joining together the DOJ, DOD, DOS, DOE, and the CIA to conduct counterintelligence activities. 04 USC Title 50 Chap 15 §402
According to the Department of Defense (a central member of the National Counterintelligence Executive), CI is defined as:
“activities conducted to identify, deceive, exploit, disrupt foreign intelligence activities” 
The FBI has primary responsibility for CI activities conducted within the US. Coordination for CI activities with the FBI and DoD is is handled by the Attorney General Loretta Lynch and Secretary of Defense Ash Carter. 
While the CIA is primarily responsible for conducting CI outside the US, the CIA can begin surveillance on a domestic target WITHOUT A WARRANT (EO 12333 AR 2-2) by directing the FBI to do it’s bidding with approval from the CIA general counsel.
The investigation into the Trump campaign was based upon faulty/fabricated intelligence alleging “collusion” with Russia and as such, investigators were permitted to “identify, deceive, exploit, disrupt” and “confound, manipulate, thwart” his campaign. 
There are a number of methods used in CI to “identify, deceive, exploit, disrupt, confound, manipulate and thwart”. 
Trump has repeatedly referred to the existence of “Spies” in his campaign. These are known as HUMINT sources — Human Intelligence.
speech or text.- Wiretaps on any phone of any suspect.- Monitoring all outgoing and incoming email messages.
This should give you a pretty good idea of what type of activities were involved in the counterintelligence investigation against the Trump campaign.
While the specifics remain classified, Spy Gate is an absolutely appropriate term.
SpieS — Plural.