The August competition was run by McDonald's Japan in conjunction with Coca-Cola and gave customers who bought large Coca-Colas the chance to win an MP3 player pre-loaded with 10 tunes.
However, after 10,000 players were sent out to consumers it was discovered that the software on the MP3 players included a dangerous "worm". This meant that when the device was plugged into a PC, the worm was activated and could steal personal data from computer hard-drives, such as usernames and passwords.
In response, McDonald's has launched a product recall, apologised for the crisis and set up a telephone helpline advising how customers can cleanse potentially infected PCs.
Dennis Szerszen, of IT security specialist SecureWave, said that McDonald's should have been more stringent before sending out the MP3 players.
"For free MP3 players, or any given technology for that matter, it's important to go through some measure of assurance that they cannot harm those that they are intended to amuse and entice," he said.
"For MP3 players, it would be a matter of assuring that they are physically safe to their intended users, then doing some level of testing to assure that they are free from any malicious threats."
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