TOU

The moment a system acts on a condition, the second half of a TOCTOU race condition.

Time-of-use is the instant a program actually uses a resource it checked earlier, completing the pair in a time-of-check to time-of-use (TOCTOU) race condition. If the resource is swapped or altered between the check and the use, the program operates on attacker-controlled state, which can lead to privilege escalation or unauthorized file access. Eliminating the window by binding the check and the action to the same handle, or using atomic operations and locking, mitigates it. On the exam, TOU is the use half of the TOCTOU race condition that TOC begins.