DETROIT (WWJ) – Target and Marriott have joined the list of companies that includes Best Buy, Citigroup , TiVo and many others, that say their customers files may have been stolen by hackers who got into the data bank of an online marketer.

Patrick Bennett from the Better Business Bureau says never trust an email that asks for personal information.

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“Legitimate companies won’t ask for financial or personal information through an email. Never click on a link that could expand a virus, hackers could get into your system and (it’s) a way for them to get your personal/financial information if you do click on that link or open any attachment associated with that email,” says Bennett.

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“From what I understand it keeps growing by the hour, it sounds like thousands have, the emails have been taken. Take precautions when you open up your email, and look at your email. Make sure that your computer is protected as well with secure firewall and updated anti-virus and anti-spyware,” says Bennett.

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Last week, a computer hacker penetrated the online marketer Epsilon, which controls the customer email databases for dozens of major corporations from Citigroup to Walgreens.