The letter to Holder from committee Chairman Bob Goodlatte of Virginia and Rep. James Sensenbrenner of Wisconsin noted that the affidavit for the search warrant for Rosen's phone, e-mail and security badge information only became public after the May 15 hearing.

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Responding to the information in the e-mails, the Department of Homeland Security said some of them are not consistent with the facts and give only a small glimpse of a much larger picture.

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Mobile users can also be duped through so-called "smishing" -- a combination of the words SMS and phishing -- where a user receives a text message asking for personal information like a credit card number, e-mail address or social security number.

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To make a purchase on a website, a MasterPass user would enter a password on the checkout page of a merchant who has installed the service as a payment option instead of typing in their card number, security code and other information that experts say slows down e-commerce transactions.

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But in the mobile age, it's easier to share intimate pieces of information like photos and videos, as well as equally sensitive information such as e-mail passwords, banking logins, health insurance identification and Social Security numbers.

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