Documentation

You can view the documentation below, or browse our GitHub Repository, where you can contribute to user manual and FAQ.

General | Installing ClamAV | How to Report A Bug | Miscellaneous FAQ | ClamAV Virus Database FAQ | End of Life Policy (EOL) | Potentially Unwanted Applications (PUA) | Mailing Lists FAQ | Troubleshooting FAQ | Safebrowsing | Upgrading ClamAV | ClamAV on Microsoft Windows FAQ | Which Version of ClamAV should I use? | Uninstalling ClamAV | ClamAV Overview | Interpreting Scan Alerts FAQ | Freshclam FAQ | How do I ignore a ClamAV signature?

Manual | Clam AntiVirus User Manual

Manual | UserManual | Installing ClamAV on Unix / Linux / macOS from Source | Installing ClamAV on Windows | Introduction | LibClamAV | On-Access Scanning | Creating signatures for ClamAV | Usage | ClamAV Development

Manual | UserManual | Installation-Unix | Installation on Debian and Ubuntu Linux Distributions | Installation on macOS (Mac OS X) | Installation on Redhat and CentOS Linux Distributions

Manual | UserManual | Signatures | Trusted and Revoked Certificates | Body-based Signature Content Format | Bytecode Signatures | Signatures based on container metadata | Database Info | Dynamic Configuration (DCONF) | Passwords for archive files \[experimental\] | Extended signature format | File Type Magic | ClamAV File Types | Functionality Levels (FLEVELs) | File hash signatures | Logical signatures | PhishSigs | Using YARA rules in ClamAV | Allow list databases

Manual | UserManual | Usage | Configuration | Scanning | Signature Testing and Management

Additional | Microsoft Authenticode Signature Verification | Private Local Mirrors

File Type Magic

ClamAV’s primary mechanism for determining file types is to match the file with a File Type Magic signature. These file type signatures are compiled into ClamAV, and may also be overridden dynamically using the definition founds found in a *.ftm file.

The ClamAV standard signature database includes these definitions in daily.ftm.

The signature format is not too disimilar from NDB body-based signatures.

The format is:

    magictype:offset:magicbytes:name:type:type[:min_flevel[:max_flevel]]

Where:

magictype: Supported magic types include:

  • 0 - direct memory comparison of magicbytes for file types
  • 1 - The magicbytes use the body-based content matching format.
  • 4 - direct memory comparison of magicbytes for partition types (HFS+, HFSX)

offset: The offset from start of the file to match against. May be * if magictype is 1.

name: A descriptive name for the file type.

rtype: Usually CL_TYPE_ANY.

type: The CL_TYPE corresponding with the file type signature. See the CL_TYPE reference for details.

min_flevel: (optional) The minimum ClamAV engine that the file type signature works with. See the FLEVEL reference for details. To be used in the event that file type support has been recently added.

max_flevel: (optional, requires min_flevel) The maximum ClamAV engine that the file type signature works with. To be used in the event that file type support has been recently removed.

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