Not an exhaustive list, just thoughts: Ames @ CIA; Penkoskvy @ KGB; the Walker family in USA (USN?); Professor Khan, Pakistan's nuclear "father"; "Doublecross" scheme in WW2; Stalin's failure to acknowledge German build-up in 1941 and finally since you're in Australia - Japanese espionage in Malaya before WW2.

All are well covered in open sources and often controversial.

davidbfpo