In our upcoming IBM X-Force 2011 Mid-year Trend and Risk Report, we discuss in detail the different phases of the changes in spam volume and the surrounding circumstances for the first term of 2011; shown in the graph below as phase 1 to 4. In the summer, the story has continued.

During phase 4 in the graph below, which covers the mid-May to mid-August timeframe, we observed a slight recovery of the overall spam levels, but particularly at the end of this phase a strong increase in ZIP attachments in spam emails. Nevertheless, at the end of June and also in July the overall spam levels were still 50 percent below the levels of the fourth quarter of 2010. But spammers continued to work. They used the summertime to increase the overall spam levels significantly since the middle of August (beginning of phase 5). By the middle of September, observed spam volume reached 80 percent of the levels nine months ago. However, by this time, ZIP Spam had decreased.