Liverpool One shopping centre in the UK has been forced to shut down a slew of digital billboards after an unknown hacker tampered with the signage this week (29 May).
"We suggest you improve your security. Sincerely, your friendly neighbourhood hackers," a message on the Elonex-branded billboard read. Images of the alleged hack emerged on both Twitter and Reddit this week, with a number of commentators charmed by the overly polite warning.
"Our screens are operated by an external company which is currently investigating what happened as a matter of urgency," a Liverpool One spokesperson said.
"As soon as the apparent hacked message appeared on the screen, Liverpool One immediately closed it down."
The hackers' message was signed "#JFT96" which is often used as an abbreviation of "Justice for the 96" following the Hillsborough football disaster in 1989.
"We can confirm an incident occurred over the weekend on one of the 18 screens we operate at Liverpool One," a spokesman for Elonex, the UK firm which produces the LED displays, told the BBC.
"The incident appears to have been good-natured and not intended to cause offence or disruption, for which we are grateful."
The Liverpool One spokesperson claimed that no other screens in the centre were affected. However, a day later, 30 May, Liverpool-based security researcher Kevin Beaumont posted a series of images on Twitter showing a number screens at the shopping mall still offline.
The identity of the culprit remains unknown at the time of writing.
"Such polite young hackers," joked one commenter on Reddit. Another added: "That's actually pretty friendly, there's a lot worse they could have put up there."
Liverpool One has more than 170 stores, bars and restaurants, a 14- screen cinema, an indoor adventure golf course, it says on its website.
University of Surrey professor Alan Woodward told the BBC in a statement: "You might not think it matters, after all it's just an advertising billboard, but who knows what else this system is linked to. The next hacker might have darker intentions."
Almost a year to the day, a series of road signs in the US were targeted by a politically-motivated hacker and made to display messages referencing Donald Trump and Bernie Sanders. One read "Donald Trump is a shape-shifting lizard" while another said "Bernie for President".
The hack came over the Memorial Day weekend in 2016, with signs altered to state "Party Hardy Y'all" by the pranksters. Another message informed commuters: "Work is cancelled. Go back home."