In May, 2009 the electronic mailing systems of the Federal Bureau of Investigation of the United States was purportedly disrupted by a virus.
Due to this disruption, the bureau was required to temporarily close down its network (the unclassified part) causing many of the agency employees to stop using the internet emailing services. They were unable to send email to their counterparts in other law enforcement and intelligence agencies. The FBI assured the public that the shut-down was part of a necessary precautionary process. It was discovered within 48 hours the possible risks to the system and soon emailing systems were back online for the external and unclassified network.» Read more