Attack patterns have been used to specify security test cases for traditional information technology systems in order to mitigate cyber attacks. However, the attack patterns for traditional information technology systems are not directly applicable to industrial control systems. This chapter considers the differences between traditional information technology systems and industrial control systems, discusses why attack patterns for traditional information technology systems are inadequate for industrial control systems, and specifies attack patterns for industrial control systems. The attack patterns are useful for creating security test cases for assessing the security levels of industrial control systems. An elevator system case study is used to demonstrate the utility of industrial control system attack patterns in specifying security test cases.