With increase in human population and economic development, population of private vehicles on road has also increased. This has resulted in increased accident probability and fatalities on the roads. Vehicular Ad-hoc Networks (VANETs) have shown promise of bringing down road accidents and fatalities thereof by enabling communication between vehicles. VANETs also allow the road operators to control and monitor vehicles for rash driving and quick relief. However, these networks face challenges of Design, Routing, Communication and Security. Use of wireless medium for communication has left these networks vulnerable to different type of security attacks. One of the important vulnerability in such networks is caused when a malicious vehicle or RSU is able to acquire multiple identities. The attack is termed as Sybil Attack. In VANETs, a malicious vehicle may send wrong messages related to traffic, accident ahead, road closed, etc. This may force the motor driver to take a different route thus making him prone to an untoward incident. In this paper, we present a survey on different detection schemes for detecting Sybil attack. Comparison among these schemes is also presented.
Keywords: Vehicular Ad hoc Networks (VANETs), VANETs Architecture, Security Attacks, Sybil Attack detection.