You have to keep watching the Chinese market in order to find IP infringement in China. There are several methods combining online & offline that we can use to protect your brands.
Taobao, Tmall, JD
Social media monitor tools, Google Alert, Brandwatch, Redpoints, YellowBrand
Brand protection managers, product experts in your company
Professional infringement investigators outside your company
Customs will report to you when they found the counterfeit products after you registered your trademark in China.
AIC (Administration of Industry and Commerce) will report to you if AIC found counterfeit products from raids.
Quality returns (after-sale), voluntary surrenders
CTA (China Trademark Association), QBPC (Quality Brands Protection Commitee of China)
INTA (International Trademark Association), IACC (International Anti Counterfeit Coalition), ACG (the Anti-Counterfeit Group)