Den of Geek:

With private business illegal in the Soviet Union, Pajitnov was nervous about what his superiors might do if he attempted to make Tetris into a commercial piece of software.

And:

Tetris was smuggled out of the Soviet Union and into Hungary a short while later, and it was from here that Pajitnov’s game began to head across Europe. Like a virus, Tetris was spreading its addictive properties from computer to computer.

And:

Tetris was an immediate hit, earning ecstatic reviews and selling in healthy quantities. The game’s fame was spreading, but as Tetris’ name became ever more valuable, the tussle over who should own the rights to it would soon intensify.

This is a pretty interesting read. I think the story would make a great movie.