A new way to cause mischief is spreading through short-messaging service Twitter as mysterious "tweets" of blocked-out text propagate themselves and cause popup windows to open.
The hack spreading Tuesday morning is extra nefarious because the tweets activate without being clicked on -- it's enough for Web surfers to move their mouse cursors over them.
However, the hack only affects visitors to Twitter.com. Various third-party programs used to send and read tweets appear to be unaffected.
The popups can contain malicious code that could take over poorly protected computers.