"According to a report produced by anti-virus software provider Sophos, 70% of anti-virus activity in the first half of this year can be blamed on Sven Jaschan, an 18-year-old German who wrote the Netsky and Sasser worms. According to the report, "Sasser claimed the top spot of the virus chart, in spite of the raging battle between the widespread Netsky and Bagle worms."
The Register has a good summary of the
report.