Eight out of 10 computers in Thailand run counterfeit software infected by malware, according to a Microsoft survey.
The report found Thailand has the second-highest volume of malicious software among five Southeast Asian countries.
The other four countries are Indonesia, Malaysia, the Philippines and Vietnam.
The government's Thailand Computer Emergency Response Team handled more than 3 million security incidents in each of the first two months of this year.
Thailand ranks among the top countries for global phishing sources, the report said.
Vipul Sant, the director for genuine software initiative at Microsoft Asia-Pacific, said the sample from Thailand indicated 80% of computers tested are infected with malicious software, higher than the regional average of 69%.
By contrast, the infection rate for piracy stands at 78%, he said.
Vietnam has the highest volume of malicious software at 90%, followed by Thailand (80%), Indonesia (60%), Malaysia (50%) and the Philippines (40%).
The survey was conducted from December-February and covered 282 computers and DVDs.
Mr Sant said infected operating systems enable hackers to control users' computers remotely and steal personal information for financial misconduct.
Ian Guy Gillard, an executive vice-president of Bangkok Bank Plc, said phishing via fake bank websites is luring customers to conduct online transactions targeting internet banking services.
Security risks in mobile banking are growing due to the proliferation of smartphones and tablets, he said.
Mr Gillard suggested consumers use licensed software from trusted sources to avoid infection. He also urged software makers to lower their prices to stimulate legal software use.
Phaichayont Vimuktanandana, a specialist at the government's Electronic Transactions Development Agency, acknowledged that phishing in the form of fake websites and botnets to steal information is common in Thailand.
"Some 700 incidents were officially reported to state authorities last year," he said.
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