From Paul Flessner, VP of Database Development at Microsoft, referring to the 2003 SQL Server Slammer Worm:

“Note to self: Career advice–Don’t bring down the Internet. I got calls from Presidents of countries I didn’t know were countries”

And in fact Microsoft SQL Server security does seem to have improved considerably since then.

FWIW, Slammer had no affect on any of the systems I was responsible for at the time.