The suspension policies and internet security measures of Hong Kong Exchanges and Clearing (HKEx) are under the spotlight after a wave of cyber attacks that crashed the exchange's regulatory disclosure website last week.
Police found that overseas hackers orchestrated the attacks that began on Wednesday to block investor access to a website hosting corporate announcements.
The attacks came in the form of a so-called distributed denial-of-service attack. Such attacks aim to prevent access to a website by overwhelming its capacity to handle website traffic.
The website's crash forced the suspension in trading of seven companies with a combined market value of HK$1.5 trillion. They include HSBC, Cathay Pacific Airways and HKEx itself. Trading was also halted on a debt security and 419 warrants and derivatives linked to the suspended stocks.
Trading in the stocks were suspended, as the companies had tried to make price-sensitive announcements during the lunchtime trading break, which investors might not have seen because of the website's crash.
HKEXnews.hk, which was under attack, is the HKEx's sole official site for all regulatory filings and disclosure announcements by the city's 1,463 listed firms. That includes 5,712 other types of securities, including warrants, derivatives and bonds.
Trading in the stocks resumed after HKEx set up a backup site on Wednesday afternoon.