TFG London identified the incident at three of its UK based retail chains on Sunday. Its two other UK brands, Inside Story and White Stuff, are not affected. The company said some of its IT systems "remain unavailable" and it paused online orders as a "precautionary measure".
An "investigation is ongoing, including establishing whether any personal or other sensitive information has been compromised," the company said. If the investigation establishes that any personal information has been accessed by hackers, TFG said it would "notify affected individuals or organisations."
The company has engaged external cybersecurity specialists to contain the incident, which has been reported to the relevant UK authorities. TFG's operations in Africa and Australia run on separate systems and are not affected.
The attack on TFG London comes less than a week after a cyber-attack on the online fashion seller Asos, in which the names, addresses and recent search data of millions of customers was accessed. H&M said on Monday that it was also investigating claims its systems had been attacked, though it stated it had not found any indications its data environment was compromised.
Several other British retailers, including Marks & Spencer, the Co-op, and Harrods, were hit by damaging cyber incidents last year. M&S and the Co-op faced stock shortages, and M&S was forced to shut down its website for several weeks.
Marijus Briedis, chief technology officer at the digital security firm NordVPN, said the incident was "another reminder that the retail sector is firmly in hackers' sights."