If you think that the bootleg vodka is a present-day invention you were wrong. People have produced bootleg vodka since very long time. Few words about the history- modern methods don’t differ from those used centuries ago.
Basically, the method and the model remains the same: we make the mash, the fermentation occures and then the mash is boiled and the vapours liquefy in the cooler. The obtained resultant is the bootleg vodka.
The next boilings makes vodka stronger. Modern equipment allows to produce bootleg vodka with a great power even in home conditions. If we have an equipment with an alcohol column we will be able to obtain a 90% (or more!) alcohol liquid.