Haven't heard the term? Let me fill you in. Microsoft puts out its latest security updates every second Tuesday of the month. This is only significant to 95% of all PC's in the world — since that's the percentage of computers using Windows and other Microsoft applications.
Malware outlaws, who have nothing better to do than exploit code, have discovered that Microsoft programs are perhaps at their most vulnerable for hacking either the day before or after that Tuesday patch update. Security watchers now refer to this at-risk period as "Zero Day" Wednesday, as in the day after.
If you look at the calendar then that would be today; making this also a good day to update you on the slew of Microsoft security updates and warnings that have cropped up over the past week.
In addition to an emergency patch that had to be issued last week, Microsoft put out five additional patches yesterday to cover a total of seven flaws in code, five within Windows.