Well, what you really want to know is that when a quiz attempt is submitted, then it is the work of the 'right' person, and that they have not just given their username and password to some dogs-body to do the quiz on their behalf.
Some poeple think that you get worthwhile risk-reduction by adding questions to the quiz like "What was the name of your first pet dog?". This assumes that you have previously collected this information, and that your staff don't pass on this information along with username and password. Probably the only reason people do this is because they have heard of other people doing this. I have never seen any research about whether it is actually effective.
Other approches to tacking this problem include analysing the moodle logs. Moodle logs all the times and IP addresses where a quiz was attempted from. E.g. is the ip in the logs the same as the computer that users normally uses? Were they actually in an importnat meeting at the time when 'they' did the quiz. This approach ahs the advanage of not inconveniencing the user at all.
Another approach is the use the quiz 'password' features. You could set the quiz password to "I am who I say I am, and you can fire me if it turns out I am lying". Again, the question is, will that acutally stop anyone cheating.
If none of that is sufficent for you, then you are probably in to custom coding. Specifially a Quiz access rule. quizaccess_honestycheck might be a bit like what you want. You could make an access rule that requires the user to type in a value that matches a custom user profile field.
Thanks for the response, Tim. Yeah...I was thinking the same thing of those variable questions, like "what is your favorite color?" If there is no solid database with which to check it, then I could log in as "Tim Hunt" and say whatever color I want. The info I would have used would have been driver's license, social security, etc, but again...how could I be certain without sure access to the infallible proof of such information? The governing bodies who are approving my courses would like such a thing, and I will offer your suggestions of IP address and "honestycheck". Thanks, Tim.