Double blind test is an experiment where both the subject and observer are unaware that the exercise in practice is a test. Double blind testing is referred to as the gold standard of testing.
Double blind tests are used in science experiments in medicine and psychology, including theoretical and practical testing. The lack of foreknowledge in a double blind test helps avoid biases and account for other effects that might influence results such as the placebo effect, where the belief one is being treated has an effect on results itself.
In computer security, penetration testing is often done as either single or double blind testing. With single blind penetration testing, the hacking team testing an organization does so with little prior information. Once assigned a target organization, the team would draw on information from publically available sources. The team might draw on USENET, company websites, forums and domain name registration in order to help discover and exploit vulnerabilities. In a double blind penetration test, not only is the testing team not pre-prepared for the test, the defending organization’s IT team is also not informed in advance. Double blind penetration testing makes for a very effective simulation of a real world cyber attack.
Often in medical science clinical trials, a subject undergoing treatment often does not know if they are actually receiving treatment or a placebo. This test condition constitutes a single blind test. If the researcher also does not know which patient or patients are actually receiving treatment, this is a double blind test. Similarly in other sciences, a subject might belong to a double blind testing or control group and the researcher would not know.