The number of cyber-crime incidents and malicious hack attacks has fallen again year on year as it has since 2001, according to a survey by the Computer Security Institute (CSI).

Its ninth annual US computer crime and security survey, conducted with the San Francisco FBI computer intrusion squad, found that overall financial losses this year from 494 survey respondents were $141m.

This is down significantly from 530 respondents reporting $201m last year.

The study found that the most expensive computer crime during 2004 was denial of service, and that the "vast majority" of organisations in the survey did not outsource any computer security activities.

CSI director Chris Keating advised organisations to raise their level of security awareness, but noted that survey respondents appear to be getting improved results from existing information security investments.

"Their average dollar losses per year have dropped in each survey for four straight years," he said in a statement.

"Obviously, computer crime remains a serious problem and some kinds of attacks can cause ruinous financial damage.

"We do not believe that all organisations maintain the same defences as our members. Financial damages for less protected organisations are almost certainly worse.

"And hackers won't become complacent anytime soon. New attacks are devised every day, and we still have our work cut out for us.

"The message here is that it makes sense to continue our focus on adherence to sound practices, deployment of sophisticated technologies, and adequate staffing and training."