A businessman who launched cyber attacks on a Hong Kong stock exchange website last year was jailed for nine months.
Tse Man-lai, 28, was earlier convicted in the District Court of two counts of obtaining access to a computer with criminal or dishonest intent.
Tse launched denial-of-service (DoS) attacks on HKExnews, a website providing price-sensitive information of listed companies, on August 12 and 13 last year. DoS attacks aim to prevent access to a website by overwhelming its capacity to handle website traffic.
Judge Kim Longley said Tse's move "caused such concern" to seven companies, including HSBC and Cathay Pacific Airways, that they suspended trading in their shares that had a combined value of HK$1.5 trillion.
Longley accepted the defence argument that Tse accessed the site only long enough to record photographs and video footage of his attacks, with the first lasting for 390 seconds and the next one for 70 seconds.
Tse was seeking to promote his firm, Pacswitch Globe Telecom, by demonstrating that the HKExnews website remained vulnerable after undergoing two distributed denial-of-service attacks from hundreds of personal computers outside Hong Kong, the court heard earlier.
He planned to use the screen images and video he had obtained from the hacking to market a method of preventing DoS attacks, which he claimed to have invented.
The police traced the hacking to a computer used only by Tse at his Tin Shui Wai home.
Samson Tam Wai-ho, former lawmaker for the information technology sector, wrote a letter of mitigation saying Tse's work had "advanced" IT in the city.
The judge noted that there was no precedent for such a case, which he had earlier called "highly reckless".
He took into consideration that Tse was a young married man who had worked hard academically and professionally.
Senior Inspector Raymond Cao Wai-ki, of the Commercial Crime Bureau technology crime division, said outside court that although Tse's hacking did little damage to the website, his sentence "sent a clear message to the public that the internet is not a lawless territory".