Peer sampling – the capability of obtaining a random sample from a large population of peers – is a basic building block for the gossip paradigm. Current peer sampling services have been designed for ”first-class” citizens of the Internet: peers that are able to accept incoming, sporadic connections. Unfortunately, the vast majority of peers do not belong to this class, as they are behind firewalls or have private addresses. Peer sampling is thus limited to peers that are freely accessible, while the others only play a limited role. The existence of two groups, with different roles and sizes, enables one group to exploit the other. This paper introduce one of such malicious scenarios, the mosquito attack, a solution to which is proposed and evaluated.