Spam volume down in September

MessageLabs cites demise of one ISP and finds that the peak time of day for sexually explicit spam falls around the noon hour.

Spam decreased 8 percent during September, according to a report (PDF) released Monday by MessageLabs.

Among other reasons behind the decrease, the security company cited the apparent demise of California-based Intercage, an Internet service provider alleged to have possibly been used to host command and control servers for various botnets. Intercage's upstream provider, Pacific Internet Exchange, terminated service on September 20; a second upstream provider, UnitedLayer, then terminated service on September 25. During this period, MessageLabs reported a marked decrease in spam traffic.

The impact of the Intercage ISP disconnection on botnet spam relays can be seen in this graph. MessageLabs

Looking deeper into the spam traffic itself, MessageLabs found that 85 percent of sexually explicit e-mail spam is sent during the workday. A healthy 28 percent of that is sent during the lunch hours, from 11 a.m. to 1 p.m. local time. Almost all of this is blocked by corporate filters.

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