Aspects of the present disclosure relate to adaptive and user-defined security against side-channel attacks in a virtual network. Traffic in the virtual network can be monitored at the hypervisor level and network security levels, such as padding and inclusion of dummy packets in the traffic stream, may be adaptively switched based on the monitored traffic information. In addition, user-defined security policies can be input to a management console. Thus, the security levels can be adaptive to real-time traffic bandwidth usage in the network and also flexibly specified by the user/administrator, which may be more efficient.