In this type of attack, the hacker sends a specially crafted packet to the victim. To understand this, one requires to have a knowledge of the TCP/IP protocol. In order to transmit data across networks, IP packets are broken down into smaller packets. This is called fragmentation. When the packets finally reach their destination, they are re-assembled together to get the original data. In the process of fragmentation, some fields are added to the fragmented packets so that they can be tracked at the destination while reassembling. In a teardrop attack, the attacker crafts some packets that overlap with each other. Consequently, the operating system at the destination gets confused about how to reassemble the packets and hence it crashes.