Shiona McCallum
Senior technology reporter

Clearly, getting an alert like this will concern people but, at the moment, there is no confirmation that customer information has been stolen.

Receiving the notification doesn’t mean your phone has been hacked - the risk will depend on if any information was accessed by the hackers.

For now, the advice is:

• Do not click on links in the notification
• Visit Asos’s official website directly for updates
• Watch out for emails, texts or calls offering refunds, compensation or help with your account - scammers will exploit this type of incident when they know people are worried
• Try and use a different passwords for your online services
• Enable two-step verification on email and banking accounts
• Keep an eye on your online transactions for anything unusual

Imogen James
Live reporter

We're yet to hear an official response from Asos, but in the meantime I've been speaking to the retailer's online chatbot to ask whether I'm safe to use my Asos account after the pop-up message.

The bot replied: "Thanks for flagging this. We're aware of the notification and are currently investigating."

It said it had no further information to share, but would provide an update "as soon as we know more".

I was then connected to an agent, who told me they understand my concern. They added: "Please don't worry, as we're aware of this issue and it's currently being looked into."

Joe Tidy
Cyber correspondent

The company has been linked to incidents targeting services including Ticketmaster and Santander.

It is, however, unusual that any potential data breach would be revealed quite so publicly - and for customers to be informed in this manner.

Most extortions and negotiations by cyber criminals are conducted in private, with hackers hoping their discretion will result in a quiet pay-off.

Dan Bird, from cyber security firm Horizon3, says the pop up message apparently sent by the criminals implies their access has gone beyond the Snowflake database.

"Sending a push notification to Asos's app users would require access to the company's notification system, which is separate from the Snowflake data platform the attackers claim to have compromised," he says.

"If both claims hold up, it suggests the attackers got hold of credentials that opened more than one door."

In the pop-up message, thought to have been sent by hackers, users were told the "Snowflake instance" had been "fully compromised".

Snowflake is a data storage company, whose popular tools have been used by dozens of firms for collecting, analysing and storing data.

It uses the cloud, so businesses store, manage and analyse their data in the cloud, meaning no large databases are needed on site.

This means it's easier to share data across different teams.

Its website says there are 12,062 global customers.

On social media, dozens of people have posted about receiving the message - confused as to what it means.

Although the apparent extortion message has been issued directly to customers, it is addressed to Asos' data protection officer (DPO) and IT team.

It also refers to the data storage company Snowflake, whose popular tools have been used by dozens of firms for collecting, analysing and storing data.

It is not known if ASOS is a customer of Snowflake or what data, if any, is stored with the service.

Asos users across the UK have been sent a notification from the retailer's app, apparently from hackers.

A message that appeared on phone screens on Tuesday morning says: "Dear Asos DPO and IT, we have fully compromised the Snowflake instance.

"Engage with us, or we will leak it."