Abstract: Systems and methods for an anti-virus detection module that can detect known undesired computer files in damaged archives that may be encrypted, compressed and/or password-protected are provided. According to one embodiment, a damaged archive file is received. And, without decrypting or decompressing the contents, an anti-virus detection module identifies a type and associated structure of the archive file by assuming each possible archive file type in turn and searching the archive file for descriptive information consistent with a current archive file type. Based thereon, descriptive information is obtained from the archive file describing one or more contained files within the archive file. Then, the descriptive information for each contained file is evaluated to determine if any contained files are malicious or undesired computer files. Finally, an attempt is made to prevent contained files determined to be a malicious or undesired computer file from being opened.