Cardiff sign hacked
The billboard was allegedly changed by hackers this week Pol/Twitter

A digital billboard located in the heart of Cardiff's main shopping street was reportedly taken over by a hacker this week, altered to display a variety of offensive images including a Nazi swastika, a Sharia Law warning and an image referencing George Orwell's 'Big Brother'.

Based on images currently in circulation on social media, the billboard was hacked to read: "Warning. This is a Shariah controlled zone. No alcohol. No gambling. No porn".

Tweets linked to the internet prankster messageboard 4Chan initially highlighted the incident in Wales.

"Some Anons from /pol/ were able to hack into a billboard in Cardiff, Wales. As you can see, they had a little fun," the account posted on 1 August.

Images show a slew of memes were posted, including Pepe the Frog which has increasingly become a symbol used by the so-called "alt-right" political movement.

The billboard is operated and managed by a company called BlowUP media, which has not yet issued an official comment on the alleged hacking attack.

Responding to comments on Twitter, the digital advertising company told one user: "Thanks, our team are working on finding out what happened."

When contacted by IBTimes UK, BlowUp media declined to comment.

A spokesperson for the South Wales Police said law enforcement was investigating the incident after receiving a number of calls from the concerned public.

"On Tuesday evening South Wales Police received a number of calls relating to concerns regarding messages being displayed on the screens in Queen Street, Cardiff," a statement read. "We alerted the city council and will investigate any crimes which may have been committed."

A spokesman for Cardiff council told Wales Online: "The council has contacted the company that own and operate the advertising screen. The screen was switched off at midnight on Tuesday night."

Billboard hacking is not uncommon. In May this year, Liverpool One shopping centre in the UK was forced to shut down billboards after an unknown culprit tampered with digital signage. "We suggest you improve your security. Sincerely, your friendly neighbourhood hackers," it read.