These critters have plagued us for a few weeks.. they really got bad the last week of September.  They are STINKBUGS.  Named that because if they become agitated, they let off a bomb of stink that is just plain gross!   I found out how to shoot them down, but some days it was a losing battle. 
1c dawn dish detergent- the blue one- in a spray bottle
fill the sprayer with water
Shoot 'em down!  They drop within a minute and are dead.. and then I sweep them off the porch.
Some of the little rascals get inside the house.. not harmful to humans particularly, and they don't breed indoors- they simply want to winter over somewhere warm.  I'd buy them a ticket to Florida, but its easier just to brush them onto a piece of paper and flush them down the commode or the sink with plenty of hot water if you use the sink.