# Signature Testing and Management
 

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 - [freshclam](#freshclam)
 - [sigtool](#sigtool)
 - [clambc](#clambc)
 
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 ## freshclam
 

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 The tool `freshclam` is used to download and update ClamAV’s official virus signature databases. While easy to use in its base configuration, `freshclam` does require a working [`freshclam.conf` configuration file](Configuration.md#freshclam) to run (the location of which can be passed in via command line if the default search location does not fit your needs).

 
 Once you have a valid configuration file, you can invoke freshclam with the following command:
 
 > $ freshclam
 
 By default, `freshclam` will then attempt to connect to ClamAV's virus signature database distribution network. If no databases exist in the directory specified, `freshclam` will do a fresh download of the requested databases. Otherwise, `freshclam` will attempt to update existing databases, pairing them against downloaded cdiffs. If a database is found to be corrupted, it is not updated and instead replaced with a fresh download.
 

 Of course, all this behaviour--and more--can be changed to suit your needs by [modifying `freshclam.conf` and/or using various command line options](Configuration.md#freshclamconf).

 
 You can find more information about freshclam with the commands:
 
 > $ man freshclam
 
 and
 
 > $ freshclam --help
 

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 ## sigtool
 

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 ClamAV provides `sigtool` as a command-line testing tool for assisting users in their efforts creating and working with virus signatures. While sigtool has many uses--including crafting signatures--of particular note, is sigtool's ability to help users and analysts in determining if a file detected by *libclamav*'s virus signatures is a false positive.
 
 This can be accomplished by using the command:
 
 > $ sigtool --unpack=FILE
 
 Where FILE points to your virus signature databases. Then, once `sigtool` has finished unpacking the database into the directory from which you ran the command, you can search for the offending signature name (provided either by [`clamscan`](./Scanning.md#clamscan) scan reports or [`clamd`](./Scanning.md#clamd) logs). As an example:
 
 > $ grep "Win.Test.EICAR" ./*
 
 Or, do all that in one step with:
 
 > $ sigtool --find="Win.Test.EICAR"
 
 This should give you the offending signature(s) in question, which can then be included as part of your [false positive report](https://www.clamav.net/reports/fp).
 
 To learn more in depth information on how `sigtool` can be used to help create virus signatures and work with malicious (and non-malicious) files please reference the many online tutorials on the topic.
 
 Otherwise, information on available sigtool functions can be easily referenced with:
 
 > $ sigtool --help
 
 and
 
 > $ man sigtool
 

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 ## clambc
 

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 `clambc` is Clam Anti-Virus’ bytecode signature testing tool. It can be used to test newly crafted bytecode signatures or to help verify existing bytecode is executing against a sample as expected.
 
 For more detailed help, please use:
 
 > $ man clambc
 
 or
 
 > $ clambc --help