The story is the same in all the cases: residents used their debit cards at a local business and then noticed large ATM withdrawals from their bank accounts.
"They did one charge on Sunday. That's actually when I shopped at the store, Sunday morning," identity theft victim Barb Bliefernich told ABC7 Chicago.
Bliefernich says she has only used cash and credit cards since she became one of at least 200 victims in the northwest suburbs to have their debit card numbers stolen and hundreds of dollars drained from their bank accounts.
"I feel very violated. It's something you read about and see on TV, but you really never think that's going to happen to you, and now it has," Bliefernich said.
Bliefernich's bank reimbursed her the $1,500 thieves robbed her of with three separate out-of-state ATM withdrawals.
Consumers in Wheeling and Buffalo Grove were targeted. Area resident George Gilbert says although he's not a victim, his bank issued him a new debit card anyway.
"I'm worried about that because of the pin number. Even with a new card, you could have the same problem," Gilbert said.
Police say they are not sure who is responsible for the illegal activity but say all the victims used their debit cards at a local business.
Batavia-based national grocery store chain Aldi issued a statement Friday acknowledging they were recently notified that the security of a limited number of debit card terminals at some stores may have been compromised, and they've removed terminals that may have been affected.
The FBI is investigating as some security experts look to technology to stop fraud. A California-based security company says its Magneprint's system uses a card's magnetic stripe like a fingerprint to prevent counterfeiting.
"We can compare to the fingerprint or the magneprint that's been on file for that card," said Andy Deignan of Magtek.
Meanwhile, detectives with the Chicago Police Department's financial crimes unit offered several ways Sunday consumers can protect themselves. Police say shoppers should use cash, don't carry pin numbers inside their wallets, carry only one card, and use a debit card as a credit card.
"There's a lot more credit card companies are much more proactive in monitoring your card activity and trying to be helpful an identify anomalies in your spending patterns," said sgt. John Lucki of the Chicago Police Department.
Detectives also warned because the holiday season is fast approaching, consumers should be on the look-out for skimming devices that are often attached to ATMs. The devices are used to download information which can then be used online or placed on a counterfeit card.