While on the metro back to our cruise ship we( 4 Americans) were almost the victims of pick pockets. We didn't even realize that we were "marked" while on the platform. A group of men (5 total) managed to get between us while on the train. The looked like average people (25-30 years old). When a older Greek woman started to yell out in perfect english, "Watch your stuff I see 3 thieves... no 5 of them". Fortunately because of the warning all of us were aware what was happening. At that point 2 of the pick pockets got off the train but 3 remained. One of the pick pockets tried to intimidate our friend by staring at him. As the 3 thieves exited the train they spit in our friends face. I guess trying to provoke him to do something. In the end nothing was stolen and we were ok. Believe the warnings about pick pockets on the Pireaus metro!