The BBC reports that the ad, which contained the text "Hey there! You found us" and says the firm is looking for "a talented engineer to develop a critical infrastructure component", was discovered by cyber-security reporter Zack Whittaker while analysing some data being sent from iPhone apps.

"As part of the stream of traffic I could see, it was connecting to this one URL – and there it was," he said.

The ad, listed under the web address us-east-1.blobstore.apple.com, now contains an error message and has since been either removed or moved elsewhere.

‘Blobstore’ is the name of a series of servers that belong to Apple.