"Spammers are finding smaller companies more susceptible to attack since they typically have fewer and less sophisticated defenses in place than larger enterprises," said Chris Smith, senior product marketing director at email service company Postini, who commissioned the survey.
The main problem that smaller companies face is the growth in directory harvest attacks (DHAs) or dictionary attacks. These occur when spammers throw emails at randomly created accounts that do not exist. Although they are stopped, the process of rejecting them saps resources.
Paul Wood, chief information security analyst at email security firm Messagelabs, agreed with the findings. "Smaller companies may not realise this is happening. We've seen examples of companies with under 200 staff receiving millions of emails through this method of bombing the domains. Often the only way it registers is through a slowing down of the server."
The survey also revealed that virus infected emails tripled during last year. 1.5 per cent of all emails now contain some form of malware.
"What we're seeing is a profound increase in sophistication and incidence," said Smith.