Internet security system and method, electronic commerce system and method

The internet security system and method in the invention employs mailing end terminal to forward data from multiple heterogeneous communication networks to receiving end server. The mailing end terminal can manipulate switch of heterogeneous communication networks or directly proceed switch of heterogeneous networks in a fixed time period, allowing receiving end server to identify the telephone number (mailing party number) forwarded by mailing party by virtue of PSTN, ISDN network, ADSL network or wireless communication network for judging if the data transaction is valid, ensuring electronic commerce security. Besides, the electronic commerce transaction system conducts through the said network so that the price labeled by seller on web site is based on time axis and the seller sets up in advance to log the starting labeled date and time of the price. The starting labeled price, price down rate (price deduction rate), and actions concerning sustaining of labeled price and price up level can automatically manipulate the labeled merchandise price on web so as to get close to the real commerce traction conditions.