The cyberattack suffered by Marks and Spencer's supermarkets has been linked to the hacking group named Scattered Spider. The attack, which has impaired the grocer's online services for customers, has yet to be resolved. The retailer has said it does not have a timeframe for when the issues, which have impacted click-and-collect and online ordering, will be fixed.

Shares in the high street staple have fallen 7% since the first reports of the attacks emerged last week. According to a report, which has not been verified, by technology industry website BleepingComputer, the attack from Scattered Spider, a sporadic group of young people from the UK and US, used a form of ransomware. Ransomeware is designed to prevent IT services from functioning until a ransom is paid to the hackers. According to BleepingComputer, ransomware hackers can demand as much as £10million to restore IT capabilities.

The report added that the hackers first gained access to the retail group's system in February.

It is reported that all of M&S' 1049 food stores have been hit and that the company has contacted CrowdStrike, Microsoft and Fenix24 to help investigate and respond to the attack.

It is unknown whether M&S was and still is being held to ransom, whether a ransom has been paid, and if so how much.

Some stores have been missing products as a result of the cyberattacks. The M&S store in Marble Arch, central London, has had empty shelves since the attack. A sign explaining the shortages read: "Please bear with us while we fix some technical issues affecting product availability".

Last week, M&S announced it had to suspend online orders due to a cyberattack on the popular retailer.

Moreover, the retailer's chief executive, Stuart Machin, wrote to customers to confirm the problem, explaining that the retailer would implement "minor, temporary changes" to in-store operations as it manages the ongoing "cyber incident."

M&S has not disclosed the nature of the cyber attack, but a spokesperson said: "As part of our proactive management of the incident, we took a decision to take some of our systems temporarily offline.

"As a result, we currently have pockets of limited availability in some stores. We are working hard to get availability back to normal across the estate."