**2.5. Routing attacks**

There are several attacks that target the network layer in WSN. For example, in the blackhole attack, adversary nodes do not forward packets completely, while it selectively forwards some packets in gray-hole attack. Another example is the sybil attack in which a node pretends multiple identities. Thus, such a node can virtually exist in different neighborhoods and drop more packets. Wormhole attack is a collusion based attack in which an agreement between two adversaries is made to perform other attacks like blackhole. In wormholes, one adversary misroutes a received packet and sends it to its partner by faking a good routing decision. A detailed explanation of these attacks and others can be found in [35].
