Ok people, just because it's a government network doesn't mean they have every one on that network as super IT geeky intelligence.
Most of the people are regular secretaries that know how to push button "A" to get "B" result, and data crunch all day long. When a prompt comes up, most are annoyed and will click madly push the cancel button to make it go away, cause they need that button "A" to continue there work. That cancel button is usually a picture and not a real prompt that then installs those pesky spyware/viruses.
Now the government IT guys can only put so many protections in place, but they can not protect against naive workers that slave through the day, then decide to load up that new virus/maleware/spyware disguised as a funny joke that is passing through the office.
@Shadow703793 please don't bash people immediately just because 40-60 year old workers, who did not grow up on computers, strain the patience of government IT network guys every day