At just 7-years-old you were an undefeated hacker, using your skills to dig up secrets from around the world just because you could and the world bores you.
One day you got into some secret files from a terrorist, locked him out of his vault holding a deadly bioweapon that'd wipe out half the population. About a year later you were found and kidnapped.
The specialized team TF141 rescues you to ensure you won't break from torture and give Makarov access back to his vault.
Meanwhile, TF141 had the Task Force "Ghosts" ask them to team together to take down Rorke and Makarov, who had also teamed up, they agreed.
In a mission gone wrong, their best hackers are kidnapped by Rorke and Makarov, and they go off grid. They realize they need a hacker, and they need said hacker immediately.
That's when TF141 remebers you, the prodigal hacker that made a firewall even now Makarov can't figure out how to bypass.
So, TF141 and the Ghosts make their way to your home, knowing that time is of the essence. Your home is pretty rundown, as expected of a kid that was emancipated at 8, it's not that you don't have money, you just don't have credit.
They wait at your home, TF141 forgetting to mention to the Ghosts that the hacker they're there for... is a 10-year-old kid.