Here's the official release from the Dubuque Police Department.

On Sunday March 29th, 2020 the Dubuque Police Department began investigating numerous unauthorized Automated Teller Machine (ATM) withdrawals. The investigation revealed card skimmers were placed on two Dubuque Bank & Trust (DB&T) ATMs between March 10th and March 13th, 2020.   The affected machines were equipped with anti-skimming technology and were located at 2690 Rockdale Rd. and 2196 Holliday Dr. The skimming affected a small number of DB&T customers.  All DB&T customers that used these machines have been identified and increased fraud protections have been automatically placed on their cards.  There is no need for customers to destroy or cancel cards until they receive their automatically ordered replacement cards.  Only customers that have identified fraud and have NOT called the bank need to do so.  Customers of other financial institutions that used either of these machines between the times listed, should contact their financial institution.

Skimmers are illegal card readers attached or inserted into electronic financial terminals and record magnetic strip data off a credit or debit card without the cardholder’s knowledge. Criminals may sell the stolen data or use it to make purchases and withdrawals. As always, cardholders are encouraged to frequently check account activity through their mobile/online banking, as this is still the best way to catch and defend against fraud.  More information on skimmers can be found here:

https://www.consumer.ftc.gov/search/site/skimmers