Cisco has reported that the Rustock botnet was the most common security issue encountered by the firm's Remote Operations Services over the past three months.
The malware is one of the most prolific spam sources on the internet. It hit its peak over the summer, and represented 21 per cent of all threat events recorded by Cisco over the quarter.
Cisco believes that Rustock is primarily used for commercial spam selling goods such as pharmaceuticals and counterfeit watches.
The company also cited the September LinkedIn malware attacks as a major security event. That attack, fuelled by the Zeus malware Trojan, accounted for more than 31 per cent of all spam at its peak.
The Stuxnet botnet, meanwhile, picked up 38 per cent of its victims in the UK and 25 per cent in Hong Kong. The Netherlands, Australia and Brunei were also popular targets.
Despite recent reports of attacks on Adobe Reader, Cisco said that overall attacks targeting the Adobe platform were down in recent months.
Reader and Acrobat flaws accounted for just one per cent of attacks in September, down from three per cent in July.
Java, meanwhile, became an increasingly popular target over the period. Attacks on the platform reached seven per cent of all web malware in September, up from five per cent in July.
Australian government to require technology and communications companies to provide access to messages
New bill avoids demanding 'backdoors' in encryption, but includes measures to compel companies to provide access to encrypted communications
Indonesian overclocker Ivan Cupa (with the aid of a lot of liquid nitrogen) achieves record overclock on AMD's latest Threadripper
Ssupermassive black hole is so big it corresponds to four per cent of the galaxy's total mass
Imminent attack will target a single bank with cloned cards used to fraudulently withdraw millions over one weekend