Of course there were the usual peaks and troughs as in every month. For instance, the recent US elections triggered a rise in politically-themed messages (from typically less that 1% to around 1.4% in October). In addition, the recent floods in India caused the Indian tax office to extend the annual filing date by 15 days - to the accompaniment of a slew of banking phishing attempts.
However, according to the report, spam represented 86.61% of all email messages, down from 89.4% in September. This actually represents very substantial reduction of 26% in total spam message counts.
Elsewhere, the report suggests total spam dropped by 22.5%, thus indicating that the previous assumption of a constant level of 'real' email is untrue and that over the period it fell by around 3%. In some ways, this echoes the premise of this morning's announcement by Facebook to suggest other methods of communication are becoming more important.
Overall, this change in spam volume can be directly attributed to the numerous botnet ring take-downs. In particular, the Bredolab botnet was disabled by Dutch authorities during October and a number of the graphs in the Symantec report suggests that although the announcement of the takedown was announced on the 26th, the actual shutdown occurred around October 11th. Although, as usual, the spammers quickly found other transmission systems and volumes recovered quickly.
It seems we're drawing slightly ahead in the struggle against spam and other more malicious email, but the fight is far from over.