You may be referring to the Insignia series by by S.J. Kincaid. It's comprised of three main books plus a prequel novella, published from 2012-2014.
This article offers a guide on the key characters in the series. The protagonist, Tom Raines, is one of several teenagers recruited by the US government to fight battles in space using unmanned drones, which the teenagers control via neural processors implanted in their brains.
Name: Thomas Raines (may respond to: Tom, Doctor, Gormless Cretin, Doctor of Gormless Cretinism)
Title: Main character
Notes: At the beginning of INSIGNIA, Tom is a drifter with his father. He’s flunking out of school and has no real skills but an ability to win video games. When he’s recruited to the Intrasolar Forces based out of the Pentagonal Spire, it’s the opportunity of a lifetime—even if he has to get a computer installed in his brain to join. Tom’s naturally independent and stubborn personality cause him no end of trouble. He makes enemies throughout INSIGNIA and VORTEX, and many of them are powerful people who can have a severe adverse impact on his life. And they do.
The US is part of an alliance with other nations such as India, Canada and various European states, and their main opposition is an alliance between Russia and China. A girl working for the Russo-Chinese side is Tom's love interest in the series.
Name: Medusa (also responds to: Yaolan, known as the Achilles of the Modern World).
Title: Tom’s love interest and the most spectacular warrior in the world
Notes: Medusa is the greatest warrior on the Russo-Chinese side. She’s also the only other person in the world who shares Tom’s ability to interface with any machine at will. She was disfigured from an accident as a child, and chose her callsign ironically. Tom is obsessed with her.
The main antagonist in the series is Joseph Vengerov, CEO of Obsidian Corp.
Name: Joseph Vengerov
Title: The Big Bad
Notes: Vengerov is the CEO of Obsidian Corp and the most powerful man in the Insigniaverse. He designed the neural processors and has killed many people testing them in his experiments. He funds both sides of the war and profits from the conflict by selling weapons. He also may or may not have a secret neural processor of his own, and an agenda for world domination.
In Book 2, Vortex, Tom gets locked out of an Obsidian Corp building in Antarctica, and loses his fingers due to the frostbite incurred.
And then the wall Tom was leaning back against abruptly swung open, and he realized it wasn’t a wall but a door, and it led straight to the outside. He realized this the same instant he crashed onto his back into a bank of icy snow. The door swung closed with a resounding clang, stranding Tom outside, without a coat, on the frozen Antarctica tundra.
FOR A FLEETING moment, Tom lay there, absolute cold soaking into the back of his flimsy suit, and then a gust of tormenting wind battered him and his brain cleared enough to register that he was outside. In a thin suit. And it wasn’t freezing cold—it was painfully, agonizingly cold.
Tom bolted to his feet and charged toward the door. His hands slipped over an icy, stinging metal surface with no handles. He had never in his life imagined it was possible to feel this cold. His ears were searing hot pokers stabbing his head, his eardrums throbbed, and the wind felt like thousands of tiny prongs jabbing viciously at him. His skull began spiking with terrible pain. Tom pounded his fist on the door.
“HEY! HEY! YOU CAN’T DO THIS! OPEN UP! OPEN THE DOOR!”
Blackburn seemed to realize what Tom was doing. “Don’t take those off here . . .” he began, but Tom had shucked off the bandage.
Now he saw what it had been hiding. Shock triggered in his gut as he saw the blackened fingers he couldn’t feel. He latched on to the other bandage with his teeth and tore it from that hand, and saw that those were blackened, too. His gut twisted. No. No, no, no . . . Wait. This couldn’t be right. He tried to curl them, tried to flex them. He shook his hands out, he pressed the fingers together. No sensation. Nothing.
A massive tourniquet seemed to be compressing him, the blood rushing in his ears. No. He needed these. He needed them for everything. Gaming. He couldn’t game without fingers. What if he didn’t become a Combatant? What if he needed to get by somehow?
Blackburn snared his wrists and set about replacing the bandages. “You’re going to get cybernetic fingers. They’ll work with the neural processor, and they’ll be almost as good as the real thing. Think of the exosuits. It’s like having one full-time.”
But exosuits hadn’t replaced something that was supposed to be there. They’d been something fun, something awesome to make him stronger, faster. They’d been something he could take off and decide not to use. Tom stared at his blackened fingers, denial blanking out his brain. This couldn’t be real.
And he and Medusa work together to prevent an asteroid from hitting the Earth in Book 3, Catalyst.
The ships ran out of armaments and hurtled straight into the asteroid. Tom could see its orbit was shallower now; it was no longer plunging in a fatal death drop straight toward the planet, but when his processor ran the calculations, he knew it was still going to hit. The atmosphere wouldn’t burn enough away.
And then when Tom jumped to another satellite, his mind met hers.
Through a haze of electronic signals, he felt her there, right there, with him. For a moment, he was blinded by a mingle of anxiety and hope, because they were all going to die, they were going to die, and he didn’t know how to fix it, but if anyone could, she could—and something about Medusa seemed to respond to that thought.
Thanks for the vote of confidence. I mean it. Tom, it’s not over.
What can we do? Tom asked.
There are thousands of nuclear missiles on the surface of the planet. I have access to the missile defense systems of every single country. No firewalls and no safety controls can keep me out. I can blow the asteroid into smaller pieces once it penetrates the atmosphere.
It won’t work, Tom thought. I heard our generals talking about it. Medusa, they can’t mobilize them fast enough.
They can’t. But I can. I know where they are and I can access, aim, and launch them near simultaneously all across the world. I’ll be fast enough. I’ll break it up into fragments small enough to burn up in the atmosphere.