Hackers have developed ways (namely Spire) for users to take advantage of Siri on the iPhone 4 and other unsupported devices. It now appears, however, that Apple may be targeting these users, and blocking unauthorized hardware from using such hacks.
iDownloadBlog reports that Apple has added a new “SetActivationToken” required for Siri to function, which disables current Siri ports. There does appear to be a fix, however. As iDownloadBlog states:
To fix these latest Siri server issues, it has been reported that a purge of the com.apple.assistant.plist file located in the var/mobile/Library/Preferences/ directory remedies the issue. I have not been able to independently confirm this, but I have heard success reports on Twitter.
It’s not at all clear that Apple is intentionally targeting unauthorized Siri usage, especially since it’s so simple to work around the new requirement.