A new critical threat to Apple's OS X operating system has surfaced that could allow attackers to compromise systems without any user interaction.

The flaw affects the way OS X handles meta data for Zip archives. The application considers the files to be safe and will automatically open them, allowing attackers to embed script code that the OS will execute without the user's knowledge.

Attackers could exploit the vulnerability to install software such as spyware or rootkits.

A system could become infected when users visit specially crafted websites or when saving any infected Zip archive. The attack requires no user interaction and uses the Terminal application, which is the OS X command shell.

Users of older versions of the operating system will first receive a warning asking whether they wish to execute the applications, but Apple removed this feature in the current 10.4 version of the operating system.

Security firm Secunia gave the flaw its highest rating of 'extremely critical', and said in an advisory that users can neutralise the threat by disabling the auto-run feature in the Safari browser. 

But the SANS Internet Storm Center later issued a warning that this workaround will fail fully to protect users.