The position is an entry-level position that consists of reading C++ code and identifying lines of code that are vulnerable to buffer overflows, out-of-bounds reads, uncontrolled format strings, and a bunch of other CWE's.
We don't expect the average candidate to be knowledgeable in the area of software security nor do we expect him or her to be an expert computer programmer; we just expect them to be able to read the code and correctly identify vulnerabilities.
I guess I could ask them the typical interview questions: reverse a string, print a list of prime numbers, etc, but I'm not sure that their ability to write code under pressure (or lack thereof) tells me anything about their ability to read code.
Should I instead focus on testing their knowledge of C++? Ask them if they understand what a pointer is and how bitwise operators work? My only concern about asking that kind of question is that I might unfairly weed out people who don't happen to have the knowledge but have the ability to acquire it. After all, it's not like they will be writing a single line of code, and it's not like we are looking only for people who already know C++, since we are willing to train the right candidate. (It is true that I could ask those questions only to those candidates who claim to know C++, but I'd like to give the same "test" to everyone.)
Should I just focus on trying to get an idea of their level of intelligence? In other words, should I get them to talk and pay attention to the way they articulate their thoughts, and so on?