useful function的用法和樣例：
例句
- In computer security, a computer program with an apparently or actually useful function that contains additional(hidden) functions that surreptitiously exploit the legitimate authorizations of the invoking process to the detriment of security.
在計算機安全學中，一種計算機程序，表面上或實際上有某種有用的功能，而含有附加的(隱藏的)可能利用了調用進程的合法特許來危害系統安全的功能。
