The yearly reported number for 2011 was 12,036: decreased 13.5 percent from 13,912 in 2010. This reported number has gradually been decreasing year by year as a virus that massively distributes a virus-contaminated e-mail to causes a large-scale infection has not existed in the past several years.

Figure1-1: Virus Report Count for Each Year

Number of viruses reported was 125 (2010: 101): of which 20 viruses were reported to IPA for the first time in 2011 (2010: 5).

Of the viruses reported, W32/Netsky was most frequently detected, followed by W32/Mydoom and W32/Autorun. Since 2004, W32/Netsky has most frequently been reported every year and its detection count is taking a large proportion of the total detection count. As for W32/Mydoom, its detection count closed to that of W32/Netsky in July and September.

Among those that marked a relatively-high detection count in a short period of time were: W32/Gammima (in July) (See Figure 2-1).

Figure2-1: Detection Count by Virus

When we look at the report count by virus, we can see that a large number of reports concerning W32/Netsky, W32/Mydoom and W32/Autorun have been submitted to IPA (See Figure 2-2).

Figure2-2: Report Count by Virus

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