The number of consumers seriously concerned about the security of online transactions is at its highest level in three years, according to the latest Unisys Security Index, released Tuesday. In the biannual survey of 1,004 consumers, which measures how safe Americans feel regarding national, financial, internet and personal security, 20 percent of respondents were “extremely concerned” about shopping or banking online, up from 16 percent in September 2009. Another 23 percent said they are “very concerned.” Meanwhile, identity theft and national security ranked as Americans’ top worries, garnering serious concern from 64 and 65 percent of respondents, respectively. — AM