Those of us who use Windows computers are well used to the nearly constant security updates required to keep our software and hardware safe. Our Apple friends are less used to it; the smaller install base (and perception of a more magnanimous corporate attitude) keeps the hackers focused on other things.
However, today Apple made available the 3.0.1 software upgrade which will fix the iPhone from being vulnerable to a hack which can leave them worthless or at least endanger them. Some information about the vulnerability from the Industry Standard:
The SMS vulnerability allowed malicious parties to send seemingly harmless text messages to an iPhone and gain access to various function of the device – such as the camera or contacts. The user would reportedly be unaware of the intrusion.
If you’ve got an iPhone, it sounds like you should install this update as soon as you can. I just found it available when I checked in iTunes for an update.