The Stuxnet worm is a rootkit exploit that targets Supervisory Control and Data Acquisition (SCADA) systems. SCADA systems are used in power, water and sewage plants, as well as in telecommunications and oil and gas refining.
Stuxnet contains code that can identify Siemens' SCADA software and then inject itself into the programmable logic controllers. Logic controllers automate the most critical parts of an industrial facility's processes, such as temperature, pressure, and the flow of water, chemicals and gasses.
Stuxnet initially exploited Windows LNK files and was spread through removable storage devices, such as USB sticks. It used four previously unknown Microsoft zero-day flaws to gain access to laptops and other machines with the goal of gaining access to the network. In response, Microsoft issued two patches and experts in SCADA security created a list of formal recommendations for facilities that use SCADA systems.
Like the Zeus banking Trojan, Stuxnet code included stolen digital certificates so the malware appeared legitimate and could avoid detection by traditional intrusion detection systems (IDS). After Stuxnet surfaced, researchers quickly began to reverse engineer the malware. It is generally believed that Stuxnet was not designed for espionage, but rather to cripple a facility's infrastructure.