As sure as the taxman cometh each year, so do the scam artists. The Internal Revenue Service is warning U.S. taxpayers to be prepared for a steady increase in scams and virus attacks via e-mail, telephone and the Web as the April 15 tax-filing deadline approaches. “We see a big upswing in complaints about these phishing emails January through April during the tax filing season,” IRS spokeswoman Nancy Mathis said. The most common type of scam arrives via e-mails claiming to come from the IRS or Treasury Department. They typically try to either scare consumers into thinking there is an error with their tax filing, or that they are eligible for a tax rebate or benefit from the government economic stimulus package that just passed on Capitol Hill. These so-called “phishing” e-mails typically arrive in an e-mail that urges users to visit a site, which in turn prompts visitors to