According to the IT security vendor's September/October monthly analysis on the state of spam on the internet, the attack saw a host of messages being distributed with a link to the ZeuS trojan.

As reported by Infosecurity at the time, because LinkedIn alerts members when other members request to join their online business friends group, users were innocently clicking on the links in their LinkedIn messages, and becoming infected.

Kaspersky Lab says that the link to the 'private messages' either led to automatically generated second-level domains in the .info zone or to hacked domains in the .com zone – in the latter case the links ended in 1.html.

Delving into the monthly report reveals there was a significant reduction in the ZeuS detections by mail anti-virus programs in the UK and US following the arrests of gang members accused of using ZeuS to steal $70 million over the last eighteen months.

The criminals, says Kaspersky, had laundered the money using fake credit cards with credentials they had acquired with the help of ZeuS.

The other big event in September was the imminent closure of the vast criminal partner program SpamIt, notorious for its commitment to the Canadian Pharmacy Viagra brand.

Maria Namestnikova, Kaspersky's senior spam analyst, said that her firm's spam-related forecasts for October are, on the one hand, positive, noting that the closure of SpamIt at the end of September will no doubt reduce the amount of Viagra adverts.

"On the other hand, the end of the month was marked by a growth in emails containing malicious code, which means the spammers have already switched from advertising pharmaceuticals to spreading malware", she said.