Forget the firewall. About 25% of malware today is designed to spread via USB storage devices that connect directly to PCs. The number comes from Panda Security, which recently surveyed 10,470 small and midsize companies -- those having up to 1,000 computers -- in 20 countries. Roughly half said that their organization had been infected by malware at least once in the previous year, and in the United States, 27% said the origin was a USB device.

"Much of the malware in circulation has been designed to distribute through these devices," said Luis Corrons, technical director of PandaLabs. "Not only does it copy itself to these gadgets, but it also runs automatically when a USB device is connected to a computer, infecting the system practically transparently to the user. This has been the case with many infections we have seen this year, such as the distribution of the Mariposa and Vodafone botnets."

Comparatively speaking, Panda found that 21% of malware originated via email and 14% from downloads or peer-to-peer networks. Infection-wise, the report also found that in the United States, the number of organizations reporting a malware infection over the past year increased slightly from 2009 to 2010, from 44% to 46%. In Europe in the same timeframe, however, infections declined from 58% to 49%.

Viruses are still the most seen type of malware, accounting for an average of 45% of the malicious code that makes its way inside the network. Spyware, meanwhile, accounts for 23%. According to the report, however, 13% of small and midsize businesses don't have any security systems in place, with 57% of them saying their organization didn't regard security as a priority. For companies with security in place, they overwhelmingly (97%) do use antivirus software, with about one-third using free antivirus software aimed at home users. Personal firewalls are also quite popular, while anti-spam technology is not.

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