Spam volumes are down sharply on their level a year ago but cybercriminals continue to hit home with easy-to-exploit vulnerabilities for Adobe and Java, the latest half-year report from security company M86 Security has said.

The company’s Labs Report for January-June 2011 confirms what every other respected source has been saying about spam levels in the aftermath of last September’s closing of pharmacy spam host,; it has declined heavily and stayed at a lower level ever since.

M86 Security’s Spam Volume Index (SVI) is now around 2000, about half the 4,000-6,000 it was during most of 2010, a positive trend aided by law enforcement disruption of several prominent botnets, especially Rustock, Mega-D and Bredolab.

As well as cutting the volume of spam traffic, disruption has also changed the content of spam, with gambling, dating, and fake goods spam challenging traditional pharma as the most common categories.

“The legal action taken by Microsoft during the Rustock takedown sent promoters of illegitimate pharmaceutical websites a strong message, perhaps making this option less attractive for spammers,” the report’s authors said. “It may be that competing affiliate programs in other categories are now more financially attractive for the spammers.”

In M86 Security’s assessment, phishing emails have become far less common, now accounting for only 1 in 1,000 spam messages sent although attachment spam still hovers at levels up to 5 percent of spam volumes.

One thing that doesn’t appear to be changing is the way that criminals continue to target software old flaws that have been around for years, most commonly in Adobe, Java and Microsoft applications.

The commonest exploit seen was an ActiveX exploit for Internet explorer from 2006, followed by a stack of flaws in Adobe Reader dating from between 2007 and 2010. Adobe’s popularity appears to be connected to its ubiquity. As individual browser flaws are patched more rapidly, this is pushing criminals to find plug-ins that are vulnerable across all browsers and Adobe fits this bill perfectly.

As Qualys revealed recently, plug-ins are also patched less assiduously than browsers, perhaps because users underestimate their security importance. This is particularly true of Adobe applications.

The company noticed a connection between countries hosting big sporting events and an increase in spam hosts targeting such occasions. South Africa saw a rise in hosts during the 2010 World Cup and the UK was now seeing a similar rise in advance of the 2012 Olympic Games. This is one issue the UK Governmen[s meticulous planning can probably do little about.