I recall reading this article about a Windows OS's, so-called, "survival time" without a Anti-virus or firewall.
I was concerned about this because it mentioned that... a Windows based XP OS can be "hacked" within half an hour without a firewall.
It also said that that's a inadequate amount of time to shield yourself... since Windows Updates can't patch within that time period.
So basically, it's not enough time for Windows Update to fully patch you during that time period. So it's "likely" to get hacked?