alt Hacker NewsServices aren't traditionally part of tariffs; tariffs apply only to physical stuff moving across borders.
That being said: I work in a services-oriented business right now "exporting" services to the U.S. and the leadership of that company is seemingly getting very worried, trying to diversify their customer base out of the U.S.
If, in the cycle of retaliatory action, they run out of ammunition with tariffs on stuff, who knows what other crazy ideas will come to the surface: Tariffs on services do come to mind, maybe restrictions around recognition/enforcement of foreign-owned intellectual property,...
Tariffs on services are much harder to enforce. There's point of entry so it's harder to check.
However, some countries have a withholding tax for services provided by foreign companies. The client is responsible for withholding the amount from any payment and paying the government. And banks play a role in the enforcement if needed.
So it can be done !