Adversarial attack 1 Attack methods Efficient strategy 1 K-shell decomposition 1 K-shells 1 Random perturbations 1 Random processes 1 Real-world networks 1 Shell structure 1 Shells (structures) 1 Simulated annealing 1 Social network 1 Structural feature 1 Structural properties 1 adversarial attack 1 k-shell decomposition 1 random perturbation 1 simulated annealing 1 structural feature 1