Do you remember that old Avis commercial about which company was the No. 1 car rental company? Avis used the slogan, "We're No. 2, but we try harder." You might say that about cyber risk and hackers, too: Cyber risk is the second biggest concern for U.S. businesses, according to the second annual Travelers Business Risk Index. But hackers are trying harder to breach data security and obtain private information, which could see the risk rise to No. 1 soon.

"The top three concerns are indicative of the ever-evolving risks that pose threats to American businesses," said Michael Klein, executive vice president and co-president of business insurance at Travelers. "Yet, when it comes to managing risk, businesses are often least prepared for their most worrisome concerns. Fortunately, many of these risks can be mitigated and resources are available to help businesses of any size stay protected."

Business leaders seem to be more optimistic than they were last year, however. Fewer survey respondents reported concerns about the economy and fewer believe the world is becoming riskier.