What's the Name of That Book??? discussion

The First book starts with some teens (at least two males) exploring an abandoned factory where, in the basement, they find a futuristic computer system, still powered. While playing with it, they discover that a girl is trapped inside the computer's simulation. After that I only remember some small parts of the book/following books, but I especially remember that:
After a few days they manage to free the girl, but she doesn't remember how she got there and remembers very little about her previous life. But they later discover that she was put there by her father (creator of the virtual reality simulation program) around 20 years before, to save her from a criminal organization that killed him in a shootout in the abandoned factory (this is confirmed by a ruined VHS tape registered by her father, that they find in a secret room in her old house). Of the rest of the books, I only remember they go around the world (pretty sure at some point they go to Paris) to fight this organization and discover what they were doing 20 years before that with the "virtual reality simulation" technology the girl got trapped in.

I read this book series (and probably I never completed it, I don't remember any ending) around 2013-15, and it was written in Italian language (probably in the mid 2000s, since one of the character has a Pda and VHS tapes are considered an "old technology" by the characters). The cover of the first book, if I remember correctly, shows the main characters inside a tunnel made of pipes and wires, and everything should have a dark blue/purple color.