Small businesses with fewer than 250 employees were the target of 31 percent of such attacks, a threefold increase from 2011.
"While small businesses may feel they are immune to targeted attacks, cybercriminals are enticed by these organizations’ bank account information, customer data and intellectual property," the company states.
Manufacturing supplanted government as the leading industry targeted for attacks in 2012, and the most commonly targeted victims of such attacks were knowledge workers at 27 percent, followed by sales personnel at 24 percent.
The company also found that Web-based attacks increased by 30 percent in 2012, with many of those attacks originating from the compromised Web sites of small businesses.
Mobile malware surged by 58 percent in 2012, with 32 percent of all mobile threats aimed at stealing information such as e-mail addresses and phone numbers.
"This year’s ISTR shows that cybercriminals aren't slowing down, and they continue to devise new ways to steal information from organizations of all sizes," Symantec chief technology officer Stephen Trilling said in a statement. "The sophistication of attacks coupled with today’s IT complexities, such as virtualization, mobility and cloud, require organizations to remain proactive and use 'defense in depth' security measures to stay ahead of attacks."