Owners of iPhones and iPads have been warned their devices could be targeted by a hacker who is freezing iOS devices and demanding a ransom.
The majority of the attacks have taken place in Australia but other instances have happened in the UK and elsewhere in Europe.
The hacker goes under the name of OIeg Pliss – a San Francisco software engineer – but this is almost certainly a pseudonym, albeit one belonging to someone familiar with technology.
The hacker exploits the Find My iPhone feature to lock stolen devices remotely. Users have been told to send ransoms of between A$50 and A$100 (up to £55) to have their devices unlocked. Numerous attacks were described on Apple's official support forums on Tuesday morning. Some users regained the use of their devices after speaking to Apple.
Attacks don't appear to be limited to a single network operator although several victims admit to not having their device passcode-protected.
Apple said customers whose devices were remotely locked were victims of a phishing attack, not a hack of its iCloud servers. It advised affected users to change their Apple ID passwords as soon as possible.