Active Bot-Infected Computers by Day

Between July 1 and December 31, 2007, an average 61,940 active bot-infected computers were observed each day, a 17% increase from the previous reporting period. An active bot-infected computer is one that carries out an average of at least one attack per day. This does not have to be continuous; rather, a single computer can be active on a number of different days. During this period 5,060,187 distinct bot-infected computers were observed, only a one percentage point increase from the first six months of 2007. A distinct bot-infected computer is a distinct computer that was active at least once during the period.

Source: Symantec Internet Security Threat Report, Vol. XIII