Fifteen people have been arrested, including four in the UK, inconnection with the hijacking of computers.
Police say the individuals were using software designed to remotely control computers - allowing for the stealing of information.
The other arrests were made in Estonia, France, Romania, Latvia, Italy, and Norway.
The practice, which in some instances can grant access to a victim's webcam, is known as "Ratting".
The phrase takes its name from the malicious software used to gain control - Remote Access Trojans (Rats).
Using Rats to view people through their own webcams, without their knowledge, is becoming "increasingly common" according to the UK government-backed Get Safe Online advice website.
The National Crime Agency (NCA) said it arrested two 33-year-old men, and a 30-year-old woman, in Leeds.
A 20-year-old man was arrested in Chatham, Kent, while a 19-year-old man had his home searched in Liverpool and was brought in for "voluntary questioning".
They are all accused of knowingly using Rats to spy on multiple targets.
"Victims are typically infected by being convinced to click on a link purporting to be a picture or video, or disguised as a legitimate file, but is instead an installer for the Rat," the NCA explained in a statement.
"In many cases, those who unwittingly install such trojans will have no indication that their machine is infected."