A false negative is the opposite of a false positive. A false negative occurs when Bitdefender fails to detect an infection.
Bitdefender detects about 99.51% of viruses in the wild, so it is possible, although very unlikely, that a virus will get past its filters. This happens mainly because new malware is released continuously and there is a time gap between the moment a virus is created and the moment we add detection for it.
Other situations concern PUA/PUP software installed with other bundled programs. In such cases, when you agree to a license agreement to load the bundled pack, Bitdefender (and any industry security solution for that matter) will not mark the program as malware because it is installed with the user’s consent.
If you suspect a false negative, submit it to Bitdefender Labs for further analysis via https://www.bitdefender.com/submit.
Once confirmed, false negatives are corrected within hours via an automatic update of Bitdefender.