In 2010, Stuxnet was discovered by the world as one of the first covert Cyber weapons. Stuxnet was a computer virus that targeted the centrifuges used to enrich uranium in Iran's covert nuclear weapons program.
The attack was complex and comprehensive in that it targeted several zero day exploits, required overcoming an air gapped network, targeted SCADA devices and presented misleading information to hide its activities.
It is estimated the damage caused by Stuxnet set back Iran's enrichment program by 18 months.
Wired and TechRepublic have authoritative articles:
- Wired - An Unprecedented Look at Stuxnet: the World's First Digital Weapon
- TechRepublic - Stuxnet: The smart person's guide
This nation state attack is an example of both the complexity of these types of attacks and their impact. YouTube has a good video about the entire event.