As the Hong Kong government asks the US to clarify Edward Snowden's claims of hacking in the city, an internet security expert says it's tough to trace when hackers attack, where they operate from and what information they steal.
"Logins would be completely erased by hackers after they get what they want," said Matthew Wong Yun-lam, a security consultant for US-based internet security firm FireEye.
If the Hong Kong government was using a US-developed computer operating system, such as Microsoft Windows, a US hacker would likely know how to break into it in the most discreet way.
"If the product is developed and hacked by the same bunch of people, they know where the back doors of the system are and know exactly how to overwrite the logins," said Wong. "Basically, you just can't follow up on the hack."
Among Snowden's claims was that leading US IT firms shared information, including vulnerabilities in their products, with the government.
As well as public officials, Snowden said the US launched hacking attacks on business targets in Hong Kong. Wong said over 90 per cent of his clients locally had computers compromised without their knowledge.
"Unlike foreign companies, local companies lack information security awareness, putting themselves at risk of being attacked by hackers," said Wong, whose company set up a branch in Hong Kong in February.
He said even if hackers found no useful information on a system, they might "manipulate the IT resources the hacked systems have, to attack other computers", making it difficult to trace who is really the culprit.
Leung Siu-cheong, senior consultant at the Computer Emergency Response Team Co-ordination Centre - set up by the Productivity Council to deal with computer crises - said cybersecurity cases reported to the centre rose 30 per cent last year to 1,050. He said the numbers had not increased dramatically since Snowden's claims. "The government hasn't sought help or advice from us," Leung said.
Meanwhile, Secretary for Security Lai Tung-kwok said the government had not asked internet service providers to give it access to information directly from their servers, as the US has been accused of doing.
Lai told lawmakers there were several laws protecting the security of Hongkongers' information online and against hacking. The issue of diplomatic immunity for overseas government agencies would be decided on a case-by-case basis.