Less than 6 percent of emails sent to businesses over over the last quarter, July through September, were legitimate correspondence. The rest were spam or malware.

PandaLabs, the analysis division of Panda Security, studied a sample of 123 million emails sent through their own TrustLayer Mail filter.

They found that 1.43 percent of all emails contained malware, including Netsky.P, Spamtaload.DO and SpamtaLoad.CZ.

The year so far:

Month ‚  ‚  ‚ ‚  spam‚ ‚ ‚ ‚ ‚ ‚  % infected
January‚ ‚ ‚ ‚ ‚  76.27‚ ‚ ‚ ‚ ‚ ‚ ‚  1.84
February‚ ‚ ‚ ‚  87.83‚ ‚ ‚ ‚ ‚ ‚ ‚  3.08
March‚ ‚ ‚ ‚ ‚ ‚ ‚  86.51‚ ‚ ‚ ‚ ‚ ‚ ‚  1.32
April‚ ‚ ‚ ‚ ‚ ‚ ‚  94.75‚ ‚ ‚ ‚ ‚ ‚ ‚  0.88
May‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚  94.71‚ ‚ ‚ ‚ ‚ ‚ ‚  0.97
June‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚  93.35‚ ‚ ‚ ‚ ‚ ‚ ‚  0.87
July‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚  90.43‚ ‚ ‚ ‚ ‚ ‚ ‚  0.98
August‚ ‚ ‚ ‚ ‚ ‚  93.01‚ ‚ ‚ ‚ ‚ ‚ ‚  0.99
September‚ ‚ ‚  91.89‚ ‚ ‚ ‚ ‚ ‚ ‚  2.34

“The percentage of infected emails increased significantly in September, to more than double the levels that we had witnessed in previous months. This could be related to the financial crisis, as cyber-crooks step up attacks to enhance their chances of success and avoid the effects of the economic recession,” says Panda’s Ryan Sherstobitoff.

PandaLabs found 91.77 percent of emails delivered to business inboxes were spam. This number peaked in August when more than 93 percent of mail traffic analyzed by Panda Security was cataloged as spam.

Much of this illicit traffic was sent from computers infected with bots, a type of malicious code that allows cyber-crooks to take remote control of compromised systems. Once a computer has been infected, it becomes what is colloquially known as a ‘zombie’. These ‘zombie’ computers, under the control of cybercriminals, are then networked together to form ‘botnets’ which are used for a range of malicious activities that includes sending spam. In the last three months alone, over 330,000 new zombies were activated each day.

Top spam topics:

Subject‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚  Percentage
Sexual enhancers‚ ‚ ‚ ‚ ‚  23%
Pharmaceuticals‚ ‚ ‚ ‚ ‚ ‚  19%
Loans‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚  12%
Replicas‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚  10%
Pornography‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚  8%
Other‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚ ‚  18%

New spam trends:

The third quarter of 2008 saw the expansion of the use of .swf (Flash) files to dodge anti-spam filters. This particular strategy involves including links in junk mail with interesting news headlines or erotic photos that then connect to an .swf file. The files themselves are generally hosted on legitimate websites but are actually designed to redirect users to the web page that cyber crooks want to advertise. The most common sites involved in this scheme were fake online pharmacies.

Another popular scam that arose in the third quarter was the use of vertical writing and hidden characters to trick content-based anti-spam engines. The technique involves writing messages vertically instead of horizontally to avoid being caught before it can appear in a user’s inbox. Also included in these emails is an additional message contained in white font that can only be seen once the user selects the content of the mail.

For more information about the latest spam trends, consult the quarterly report published by Commtouch and Panda Security.

About The Author

John Guilfoil is the editor-in-chief of Blast: Boston's Online Magazine and the Blast Magazine Network. He can be reached at [email protected]. Tweet @johnguilfoil.

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