A US official has emphasised the growing threat of cyber-crime towards the States and the western world, at an event discussing botnets and other online security challenges.

Janet Napolitano, Secretary of Homeland Security, said that "the greatest threats in actual activity we've seen aimed at the West and the United States has been in the cyber-arena", in addition to "al Qaeda and al Qaeda-related groups".

The comments highlight the increasing trend of political sparring and espionage proliferating on the Web. The Flame virus, believed to be driven by a western government, continues to grab headlines, while Google has introduced a tool to warn users of state-sponsored attacks on their accounts.

Napolitano said the government is taking steps to be "proactive instead of reactive" in combating the new threats, adding that the worldwide cost of tackling cyber-crime - an estimated $388 billion (£250 billion) - is "already outstripping [the cost of tackling] traditional narcotics".

A White House plan code-named Olympic Games was launched to infect Iran's nuclear program at the beginning of the Obama administration, though Washington denies the Flame virus, also targeting Iran, was part of the project, after it was found to have existed for a number of years.