China has emerged as the second largest nation in terms of number of computers with multiple infections in government and critical infrastructure sectors, a study by US-based Internet security software maker Symantec Corp said.

The high number of attacks originating in China is likely due to the rapid broadband Internet growth, it said.

India has been ranked at sixth position in country-wise list for computers with multiple infections mentioned in the study - Government Internet Security Threat Report. The list has been topped by the US.

Aerospace, telecom, healthcare, financial services and agriculture were included among critical infrastructure sectors for the study.

Telecom accounted for 90 per cent of all malicious activity originating from critical infrastructure sectors and hacking was responsible for 73 per cent of identities exposed.

China was also named in top three countries in five other metrics -- malicious activity by country, top countries targeted by DoS attacks, Bot-infected computers by country, top countries of attack origin, computers with multiple infections by country.

Regarding India, the report pointed out that the presence of Rontokbro worm was seen more in India despite the infected email being in Indonesia.

Substantial trade activities take place between the two countries and it is likely that many enterprise users in Indonesia communicate with counterparts in India by email.

"Rontokbro sends its email messages to all the addresses it gathers from files on a compromised computer, it stands to reason that this worm was sent to many Indian users from business contacts in Indonesia," the report said.

Rontokbro is one of the top 10 malicious code samples resulting in potential infections in the EMEA region.

The top two countries with the highest number of internet users worldwide, United States and China, were found to be more vulnerable to internet security threats. Both nations found themselves among the top three in most of the categories including malicious activity by country, top countries targeted by DoS attacks and Bot-infected computers.

The US accounted for the biggest share of all malicious activity (30 per cent), while Israel had highest malicious activity per internet user. China, accounting for 13 per cent internet users across the world, had the highest number of Bot-infected computers and accounted for 29 per cent of the worldwide total.

However, the report notes that percentage of Bot-infected computers in China has come down in the first half of 2007, compared to the same period a year ago, indicating a rising security awareness among the internet users there.

In terms of top countries of attack-origin worldwide, the US (25 per cent) was ranked first, followed by China (13 per cent).

The report noted that higher attack-origins in the US and China indicated towards computer crime laws not effectively deterring computer criminals and attackers.