In the latest installment of its State of Spam report, the company claims that malware-laden messages are becoming far more common than they were in the first half of the year.
Symantec now estimates that some 1.2 per cent of all email messages sent contains a malicious payload.
Overall, the company found that spam comprises some 78 per cent of the global email volume.
While attached .zip and .rar archives were the most popular method for spreading malware, researchers also found that embedding attack code within the source code of the message itself was also becoming popular.
"The increase began in May 2008 and continues to the present," the company said in the report.
"During this period, there has also been an increase in email messages carrying malware payloads, not just links to malicious code."
The majority of the malicious payloads found were generic trojan horse, downloader and info-stealing applications. Trojan horse attacks comprised 13.4 per cent of malware detections, while downloads and infostealers logged 11.8 and 11.1 per cent respectively.
The Pandex trojan was the most popular single piece of spammed malware, followed by W32.IRCBot and the Goldun trojan.
China was the most popular origin for the malicious spam messages, followed by the Republic of Korea, the United States, Thailand and Vietnam.