ASOS customers issued security warning after alleged hackers sent threatening message

ASOS customers have been sent an eerie message via the fashion retailer's app announcing that it had been hacked.

ASOS is thought to have as many as 17 million users globally, many of whom received today's message (October 6).

The message read: "Dear ASOS DPO and IT, we have full compromised the Snowflake instance. Engage with us, or we will leak it."

This was followed by a link to the apparent hackers' Telegram link.

The alleged hack refers to cloud firm Snowflake, which stores data for many major companies. It is not known if ASOS is a customer of Snowflake or what data, if any, is stored with the service.

It has been the reported subject of a number of data breaches in recent years, including an attack on Ticketmaster which saw customer details stolen.

Online retailer ASOS has millions of customers worldwide (Nathan Stirk/Getty Images)

'This is a deeply serious attack'

Shares in the company tumbled by more than 10 percent this morning as a result of the apparent hack.

While it's a global brand, the UK is the group’s largest market and represents 49 percent of all revenues in the first half of the latest financial year.

Experts have called the ordeal a 'deeply serious attack'. Charlotte Wilson, head of enterprise at cyber-security firm Check Point, told BBC News: "If confirmed, this is a deeply serious attack because the hackers appear to have done something particularly brazen: turned ASOS' own app into their ransom note.

"Millions of people trust notifications from apps on their phones because they are supposed to come directly from the company."

Another cyber security expert expressed fears that their access has gone beyond Snowflake's database in light of them being able to send a push notification on ASOS' app.

Some consumers with the ASOS app received this message (PA Media)

"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," said Dan Bird from cyber security firm Horizon3.

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

ASOS is yet to publicly comment on the alleged hack.

Pete Membrey, chief research officer at ExpressVPN, has advised that people 'hold off' from making any ASOS purchases today.

Speaking to Sky News, the tech expert shared: "Personally, I'd hold off on making any new purchases through the ASOS app or website until the company says more.

"There's no public information yet on the level or scope of the attack, so we just don't know what's at risk and what isn't."

People are being advised to change their ASOS account passwords (Dinendra Haria/SOPA Images/LightRocket via Getty Images)

'A bit of caution is the sensible option'

He went on to say that while the app is still up and running, we 'can't tell what's going on behind the scenes'.

"This could change very quickly. ASOS might confirm shortly that it's a limited incident that doesn't affect customer logins or payments," Mebrey continued. "But until we have that information, a bit of caution is the sensible option."

He proceeded to urge people to go onto their ASOS accounts and change their passwords 'just in case'.