He is titled Agent Silent G for the silent g in "gnu". Coincidentally, Agent Silent G doesn't seem to make a sound.
In Brazil, the g in "gnu" is pronounced so Newton had his name changed to Gnewton.
Newton's identity remained secret until Doofenshmirtz put it up on his blog.
According to his secret file, he tends to keep to himself. He is known for his full luxurious beard. And he is looking for a new secret identity since it was revealed by Dr. Doofenshirtz.(Where's My Perry?)