Computer hackers have posted instructions on the Internet on how to break into people's confidential files. Two new hacking programmes, which could cause havoc for businesses, have affected two companies in Hong Kong in the past month, according to computer experts. They said that businesses should be on the alert for the computer hacker programmes which can allow a hacker on the Internet to control a firm's computer system. One web site gives people detailed instructions on how to 'control' the target computer. It says it can be used 'just to have some fun with your friends on the local network or even on the global Internet'. John Lauderdale, a manager at PricewaterhouseCoopers' Global Risk Management Solutions, said he had come across several cases of businesses being affected in the past month. He said hacking into a computer over the Internet used to require detailed knowledge about computers and networks. 'But now new Windows-based programmes . . . make it very easy for even an unsophisticated user to gain access,' he said. 'It is easy for an attacker to send an e-mail to a company employee and this may contain a programme that allows an intruder to gain access or control of that computer.' One programme can open and close CD-ROMs, swap mouse buttons, show different messages, shut down Windows, remove and close the server files, record from microphones, disable keys and kill open Windows. Mr Lauderdale said companies should realise Hong Kong's reputation as a regional banking and financial centre served to attract potential computer criminals worldwide. He urged company managers to asses their security risks and find out what security controls were available on the market.