Computer Emergency Response Team (CERT) has found a flaw in the standard used to regulate how computers communicate over the Internet, which means that basically all net-connected computers are vulnerable to hack.
The flaw lies in TCP (Transfer Control Protocol.) "TCP was designed to be a reliable protocol, and to insure that it was designed to be somewhat predictable," said a CERT official.
However, because of this predictability, it might be possible for hackers to predict which ISN number would come next, enabling them to steal emails or listen in on chats, for example. However, it is not easy to take advantage of this flaw.