It is reported that the cybersecurity incident caused issues with the tills and also resulted in stock deliveries being temporarily suspended, with longer delivery times for online orders.
Bosses at The Works – which has stores in The Bridges in Sunderland and Middleton Grange in Hartlepool – said that deliveries to stores "are expected to resume imminently" and its normal online service levels are steadily being reintroduced.
In a statement, The Works said: "There has been some limited disruption to trading and business operations, including the closure of some stores due to till issues.
"Customers can continue to shop safely at The Works, both in store and online.
"All debit and credit card payment data are processed securely outside the group's systems, via accredited third-party networks, and therefore there is no risk that this payment data has been accessed improperly."
The Works has said that a number of actions have been taken after it was alerted to the breach by its security firewall.
All internal and external access to its systems, including email, have been disabled while it works with its advisers to evaluate and rectify the situation.
Cyber security experts have also been appointed and are currently completing investigations and recovery work.
The company added that, while payment data has not been compromised, it has not yet established "the full extent to which any other data may have been affected".