Howard Carmack was found guilty of stealing the identity of two Buffalo-area residents to open internet access accounts with EarthLink, an ISP.
He was also found guilty of falsifying business records of EarthLink, when he forged the headers of e-mail sent from the EarthLink accounts.
"The guilty verdict rendered by the jury in this case shows that those engaged in identity theft and cyber-crime will be discovered prosecuted and convicted of their crimes," said State Attorney General Eliot Spitzer after the verdict.
Carmack will be sentenced on 27th May and faces between three and seven years' imprisonment. He already faces a civil injunction and last year he and others in his Buffalo spam operation were ordered to pay damages of $16.4 million after being sued by EarthLink over the sending of over 825 million illegal e-mails.