About 20 percent of universities, companies and municipal governments have had their computer systems illegally accessed during the past year, but just 5.3 percent of them alerted police, according to a survey released Thursday by the National Police Agency.

The survey was conducted between October and December and covered 327 companies, 49 universities and 29 local governments.

Among the 405 organizations, 80, or 19.8 percent, said someone had accessed their computer systems without authorization. Of those, 55 percent said their systems were infected with a virus due to the hacking and 3.8 percent said their systems were destroyed by such access.

Most of the intruders were not identified.

According to the survey, 75 percent of the organizations experiencing illegal access did not report the damage to police or an auxiliary organization of the Ministry of Economy, Trade and Industry, which deals with such cases.

Reasons cited for not reporting the intrusions were that it was not serious enough or that reporting would not solve the problem.

The survey found that 90.4 percent of the entities have taken measures against computer viruses, such as installing antivirus software.

However, many expressed a negative attitude toward taking emergency safety measures to cover the overall computer systems, saying the cost for such measures is too high and they lack the technical knowhow to set up such measures.