The virus signature, also known as virus definition, is a unique binary string that represents a part or the entirety of a computer virus. In a similar way to fingerprints, it helps identify specific viruses. Antivirus software uses virus signatures to precisely detect malicious codes.
BitDefender uses an incremental virus signature system based on two file types, cvd and ivd. The first contains the main collection of virus signatures, while the second stores only the latest updates. Once every three months, BitDefender downloads an updated version of the cvd file and ivd is reset to 0. This allows for small daily virus signatures updates.
In order to further optimize the update transfers and the scan speed, similar virus signatures are combined into a single pattern, specific for an entire virus family. This process reduces the number of virus signatures displayed in the product, without adversely affecting the virus detection.
BitDefender allows automatic download of virus signatures, or they can be downloaded as separate packages.