Starting in 1998,
U.S. government officials began noticing a pattern of probes into various
government networks, including the Pentagon, NASA, universities, research
institutions and the Department of Energy. Evidently, hackers – believed to be
located in Russia – had compromised these networks and left backdoors through
which they could secretly slip at a later time. The targets of these intrusions
were mostly unclassified but sensitive information such as military hardware
design plans, maps of military bases, and troop arrangements. The probes may
have gone on for as long as three years, making it the longest known sustained cyber-attack
on the U.S. and revealing serious lapses in U.S. cyber defense.