NEW YORK (CBS/AP) — Congressman Luis Gutierrez said Friday’s revelation that nearly 110 million American shoppers were the victims of a data breach at Target stores serves as proof more vigilance is needed all around to protect our private information.

Gutierrez was concerned, but didn’t seem surprised, after learning Target revealed the breach of credit card and debit card data during the holiday shopping season was nearly triple the original estimate of 40 million victims.

He said Congress might see what more can be done at the federal level in the wake of the massive data breach, but he said consumers also must take steps on their own to protect their personal information.

Gutierrez said shoppers should change their online passwords frequently, and shouldn’t make them obvious.

“You have a lot of large corporations that work with the defense industry, and they’re being penetrated every day, and there have to be guards put up every day,” he said. “So I think the first guard is your own personal one.”

Target said Friday that personal information — including phone numbers and email and mailing addresses — was stolen from as many as 110 million customers in its pre-Christmas data breach.

The chain also indicated its sales have been hurt by the breach, cutting its forecast for fourth-quarter earnings and a key sales barometer.

Its stock slipped in early morning trading Friday.

Experts say thieves have enough information to steal the identities of all the shoppers whose information was compromised. Anti-fraud expert Bill Kresse of St. Xavier University says consumers should be prepared to monitor their credit reports for years to come.

“If you see a request for information on you from a source that you never requested, that’s suspicious,” he tells CBS 2’s Dorothy Tucker. “That’s someone potentially trying to steal your identity.”

Target Corp. announced in December that about 40 million credit and debit cards may have been affected by a data breach that happened between Nov. 27 and Dec. 15 — just as the holiday shopping season was getting into gear.

But the net has now been cast wider, with more shoppers potentially impacted.

The company told customers Friday that its ongoing investigation of the breach has shown that more personal information had been stolen than it was aware of before and more customers were affected. It previously disclosed to customers that names, credit and debit card numbers, card expiration dates, debit-card PINs and the embedded code on the magnetic strip on the back of cards had been stolen.

“I know that it is frustrating for our guests to learn that this information was taken and we are truly sorry they are having to endure this,” Chairman, President and CEO Gregg Steinhafel said in a statement.

The company said customers won’t be liable for the cost of any fraudulent charges that stemmed from the breach.

Target said it will try to contact customers it has email addresses for to provide tips on how to safeguard against consumer scams. The company said it won’t ask customers for any personal information during its email communications.

It’s also offering a year of free credit monitoring and identity theft protection to customers that shopped at its stores. Individuals will have three months to enroll in the program. Target said it will provide more details on that next week.

Target lowered its fourth-quarter adjusted earnings guidance to a range of $1.20 to $1.30 per share, down from $1.50 to $1.60 per share.

Analysts surveyed by FactSet expect earnings of $1.24 per share.

The Minneapolis company also said that it now foresees fourth-quarter sales at stores open at least a year will be down about 2.5 percent. It previously predicted those sales would be about flat.

This figure is a closely-watched indicator of a retailer’s health. It excludes results from stores recently opened or closed.

Target cautioned that its fourth-quarter financials may include charges related to the data breach. The chain said the costs tied to the breach may have a material adverse effect on its quarterly results as well as future periods.

Shares of Target declined 32 cents to $63.03 shortly after the market opened.

The company has 1,921 stores, with 1,797 locations in the U.S. and 124 in Canada.

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