Over forty percent of IT executives at small- and medium-sized businesses say their networks are not secure, even though almost all have firewalls and anti-virus software installed, according to a recent study.

A survey of 455 SMBs by international software developer GFI also found 32 percent of companies experienced a security breach in the past year, most often due to a virus attack. Other problems included infected internet downloads and lost or stolen hardware, such as laptops.

However, email viruses aren't the only problem SMBs face, Andre Muscat, GFI's Director of Engineering, said in a statement. "While companies are aware of, and are focused on, tackling viruses and malware, they appear to be giving sparse attention to other equally dangerous threats such as data theft and leakage from endpoints such as connected USB sticks, iPods and PDAs on the network," Muscat said.

A separate survey by research and consulting firm AMI-Partners found small business spending on IT infrastructure and applications increased 16 percent this year.