If you’re the administrator of a machine that runs sendmail, there’s a nasty security problem that found its way to the surface today. Discovered by the people at ISS, the bug allows someone to compromise your machine simply by sending a specially-formatted email; firewalls aren’t going to help you on this, since it’s the contents of the email that trigger the security breach. The list of affected systems and operating systems is pretty extensive, so you might want to peruse it before assuming that you’re not vulnerable.