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What is a Time-of-Check-Time-of-Use?

Time-of-Check-Time-of-Use (TOCTOU) attacks fall under the category of a race condition (which occurs when two or more operations that should be done in sequence are attempted simultaneously). A hacker is able to access a file and make harmful changes between the time of check (first time the program accesses the file) and the time of use (when the software uses the file). The opportunity window is very short due to that near simultaneous overlap.

How to Recognize This Threat: Shared files that multiple users can access are susceptible to TOCTOU issues. A file that has been corrupted could cause a system crash or corrupt data related to the file.

How to Prevent This Threat:Ensure your network has processes in place to avoid race conditions, such as prioritizing file access so that only one user can edit the file at a time. Firewalls.com Security Operations Center experts can help. Learn about getting your firewall professionally configured.