Remember TOCTOU
Full name: Time of Check to Time of Use
Memory aid: The Check happens now; the Use happens later.
Performing a check is insufficient when the checked state can change before use.
Study area: Threats & application security · Batch 8
Relevant study for: CompTIA Security+ SY0-701 · ISC2 CISSP 2024 outline · CompTIA CySA+ · CompTIA PenTest+
Practice with exam flashcards →Cybersecurity & Identity / Knowledge library
TOCTOU — Time of Check to Time of Use
Describes a race when state changes between validation and later use.
Why learn TOCTOU — Time of Check to Time of Use?
Describes a race when state changes between validation and later use.
Where it came from
Performing a check is insufficient when the checked state can change before use.
- Memory aid (a learning cue, not the expansion): The Check happens now; the Use happens later.
Build your understanding
Work through these exercises in order. Try the task before opening a reference.
- Without looking, expand TOCTOU: Time of Check to Time of Use.
- Recall this memory aid: The Check happens now; the Use happens later.
- Explain the practical use: Describes a race when state changes between validation and later use.
- Explain this distinction: Performing a check is insufficient when the checked state can change before use.
- Identify TOCTOU in a device specification, architecture diagram, or system inventory.
Documentation and sources
- NIST cybersecurity glossary (csrc.nist.gov)