Vehicular Ad-hoc Networks (VANETs) are gaining
rapid momentum with the increasing number of vehicles on the
road. VANETs are ad-hoc networks where vehicles exchange
information about the traffic, road conditions to each other or to
the road-side infrastructures. VANETs are characterized by high
mobility and dynamic topology changes due to the high-speed
vehicles in the network. These characteristics pose security
challenges as vehicles can be conceded. It is critical to address
security for the sake of protecting private data of vehicle and to
avoid flooding of false data which defeats the purpose of
VANETs. Sybil attack is one of the attacks where a vehicle fakes
multiple vehicle identity to compromise the whole network. In this
work, a direct trust manager is introduced which derives the trust
value of each of its neighbor nodes at a regular interval of time. If
the trust value is deviated, it confirms sybil attack. The proposed
system is compared with the existing system to prove improved
sybil attack detection ratio, thus providing better security. NS2
environment is used to prove the simulation results. The
experimental results show that the attack detection ratio of
SAD-V-DTC is 5 times better than that of the existing system. The
packet delivery ratio shows an improvement of 27.27% while the
false positive shows a good increase of 65.80% than the existing
system.