There is a band of greenish looking mold on the perimeter of the brick on the front of my house. It is about 12 to 18 inches in height. Any idea?

Could it be moss? Moss can grow on damp bricks or cement?

Jack is right. It's probably a moss or fungus. Do you have a sprinkler system that fires at that height. If not it is probably a rising damp problem and you will have to get an expert in.

Moss Generally grows on the north side. Examin your house to see which side the green stuff is .If its on the north side ,then it's the beginning growth of moss. I had that same problem and used a pressure washer to spray it right off the brick ,and I have to do that annually

For any green algae or moss problem I don't use a pressure washer (too damaging). I use regular dish soap (about 1/2 cup) and one cup of chlorine bleach to a big bucket of water. I use a long handled brush and gently scrub the surface. Then I rinse with clean water from the hose. Repeat if necessary. Pressure washing can definitely damage the mortar holding the bricks. That can be expensive to repair.