Islands

Islands are named that way because their appearance looks like an island – a time zone infraction in which the middle sticks out above the others. Another term for this pattern is the head-and-shoulders pattern.

Islands are the most ambiguous scenarios because while they indicate that a problem existed in the past, it is more difficult to ascertain that condition now. A drop in outbound spam from the previous hour could mean two things:

1. The problem has been resolved and latent spam reports are still trickling in.
   
   
2. Alternatively, it could mean that there is random, hour-to-hour noise. During the next hour, the problem is easier to diagnose because a different, more telling pattern will form.

Valleys

Valleys are so-named because the visual pattern they form looks like a valley; the current run and the run from two hours ago are greater in size than the one from one hour ago.

Valleys, similar to mountains, generally give very unambiguous signals that a spam problem has occurred. It is usually a very clear signal that a sudden shift in outbound spam has occurred because the current run so greatly dwarfs the previous one.