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This was one of the first truly creative mass-mailing worms, using an extensive menu of options to fool recipients into clicking the malicious payload. It mixed and matched subjects, message bodies, attachment names, and fake assurances that the file had been scanned by a reputable antivirus program and declared clean. The author was an 18-year-old German, who had also written the infamous Sasser worm.
Netsky was annoying (one variant caused infected PCs to beep in the wee hours of the night) but not destructive. (This CA writeup has more details.)
The source code contained numerous insults aimed at other virus writers.