Doesn't work. Keychain folder automatically replaces itself after about an hour, and even when the Mac is closed and the wifi off.
Not malware, it's a Keychain problem. It's a real stupid issue on OS X. This is how you solve it.
1) Open the Library by clicking the 'Go' menu in Finder. Hold down the 'Alt' key, and Library will be visible.
2) Navigate to the folder called 'Keychains'. Open this folder.
3) Delete all folders you see in the Keychain folder. You won't be able to empty the Trash, so don't worry about trying to empty it.
4) Restart your Mac.
5) If it prompts you for a keychain at the start, click 'Create new keychain'
You'll have to re-enter saved passwords and stuff like that, but this should fix the issue.
While you're doing this, if you get the keychain error, just click 'Cancel'.