clamav

About clamav

From Debian's package description

Clam AntiVirus is an anti-virus toolkit for Unix. The main purpose of this software is the integration with mail servers (attachment scanning). The package provides a flexible and scalable multi-threaded daemon in the clamav-daemon package, a command-line scanner in the clamav package, and a tool for automatic updating via the Internet in the clamav-freshclam package. The programs are based on libclamav, which can be used by other software.

This package contains the command line interface. Features:

• built-in support for various archive formats, including Zip, Tar, Gzip, Bzip2, OLE2, Cabinet, CHM, BinHex, SIS and others;
• built-in support for almost all mail file formats;
• built-in support for ELF executables and Portable Executable files compressed with UPX, FSG, Petite, NsPack, wwpack32, MEW, Upack and obfuscated with SUE, Y0da Cryptor and others;
• built-in support for popular document formats including Microsoft Office and Mac Office files, HTML, RTF and PDF.

For scanning to work, a virus database is needed. There are two options for getting it:

• clamav-freshclam: updates the database from Internet. This is recommended with Internet access.
• clamav-data: for users without Internet access. The package is not updated once installed. The clamav-getfiles package allows creating custom packages from an Internet-connected computer.

From Debian's description of the clamav package, under that package's license.