By Patrick Temple-West WASHINGTON (Reuters) – Kev Imandoust guards his U.S. Social Security number with 25-character passwords and email encryption software. But in 2012, the San Diego accountant became one of more than a million Americans whose identities were stolen to use for tax refund fraud. When he tried to file his taxes days before the April 15 deadline two years ago, Imandoust had his return rejected by the Internal Revenue Service. Someone in Florida had filed using his name and Social Security number, the IRS said.