Race conditions

- [Instructor] Race conditions are a particularly dangerous … security flaw and require careful attention … from software developers and security professionals … in order to prevent them. … A race condition occurs when the proper functioning … of a security control depends upon the timing … of activities performed by the computer or the user. … If the timing doesn't occur as expected, … the software may behave in an unexpected manner. … A common example of a race condition … is a Time of Check to Time of Use, … or TOCTOU, vulnerability. … In a TOCTOU vulnerability, software first checks … to see whether an activity is authorized … and then waits some time before performing the action … that is authorized. … The catch it that the authorization status … might have changed during the time that elapsed. … Let's take a look at an example of a bank account. … Imagine an ATM machine that dispenses cash. … The algorithm for the machine might work … something like this. … First, the user inserts an ATM card. …