P. Shanmugaraja, D. Balamurgan, S. Chandrasekar, Security Attacks on IPv4-IPv6 Transitions-Possible Mitagation Techniques, International Journal of Soft Computing, Volume 9,Issue 2, 2014, Pages 79-84, ISSN 1816-9503, ijscomp.2014.79.84, (https://makhillpublications.co/view-article.php?doi=ijscomp.2014.79.84) Abstract: Internet protocol is the widely deployed protocol used for communication. The internet engineering task force is the organization responsible for defining the internet protocol standards. When the IETF developed IPv4, the wide growth of the internet and the security issues were not expected. Due to internet’s rapid growth IPv6 was designed. IPv6 is designed to achieve simplicity, increased routing speed, improved QOS and inbuilt security. Due to the massive growth in internet users and technology deployment of IPv6 is mandatory. Because the successor of IPv4 is not compatible, transition technologies play a key role in establishing the communication between IPv4 and IPv6. Currently, both protocol suites are needed for communication so the involvement of transition technology is also mandatory. IETF Next Generation Transition working group (NGTrans) has developed many transition technologies to enable the integration of IPv6 facilities into current infrastructure that uses IPv4. This study discusses Internet Protocol ver4 security issues, internet protocol ver6 issues and compares both the internet communication protocols. Because the transition phase involves both internet protocols, the transition phase is vulnerable to major security issues. This study synthesizes different security threats that are involved in the transition phase. Some of the Mitigation techniques for the threats are also synthesized. Keywords: Dos;IPv6;IPv4;IPSec;tunneling;transition mechanisms