HONG KONG (AP) — Wild gyrations in Hong Kong share prices are raising concerns that a new trading link with mainland China is a conduit for questionable trading practices that could undermine the city's reputation as a center of global finance. Major breaches have exposed critical data at banks, retailers, health care providers and the government, as evidenced by word this month that hackers compromised personal information of at least 4 million current and former federal employees. Faced with a constant barrage of cyberattacks, its key to stay on top of the latest threats to learn about potential vulnerabilities and effective defenses, says Rick Orloff, the head of security at e-commerce company eBay Inc.