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                        <h1 id="signature-testing-and-management"><a class="header" href="#signature-testing-and-management">Signature Testing and Management</a></h1>
<p>Table Of Contents</p>
<ul>
<li><a href="#signature-testing-and-management">Signature Testing and Management</a>
<ul>
<li><a href="#freshclam">FreshClam</a></li>
<li><a href="#sigtool">SigTool</a></li>
<li><a href="#clambc">ClamBC</a></li>
<li><a href="#next-steps">Next Steps</a></li>
<li><a href="#create-your-own-signatures">Create your own signatures</a></li>
</ul>
</li>
</ul>
<blockquote>
<p><em>Tip</em>: The commands on Windows are generally the same, but you may need to add the <code>.exe</code> extension to run the ClamAV applications.</p>
</blockquote>
<h2 id="freshclam"><a class="header" href="#freshclam">FreshClam</a></h2>
<p>Before you can start the ClamAV scanning engine (using either <code>clamd</code> or <code>clamscan</code>), you must <em>first</em> have ClamAV Virus Database (.cvd) file(s) installed in the appropriate location on your system.</p>
<p>The tool <code>freshclam</code> is used to download and update ClamAV’s official virus signature databases. While easy to use in its base configuration, <code>freshclam</code> does require a working <a href="Configuration.html#freshclamconf"><code>freshclam.conf</code> configuration file</a> to run (the location of which can be passed in via command line if the default search location does not fit your needs).</p>
<p>Once you have a valid configuration file, you can invoke FreshClam with the following command:</p>
<pre><code class="language-bash">freshclam
</code></pre>
<p>By default, <code>freshclam</code> will then attempt to connect to ClamAV's virus signature database distribution network. If no databases exist in the directory specified, <code>freshclam</code> will do a fresh download of the requested databases. Otherwise, <code>freshclam</code> 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.</p>
<p>Of course, all this behavior--and more--can be changed to suit your needs by <a href="Configuration.html#freshclamconf">modifying <code>freshclam.conf</code> and/or using various command line options</a>.</p>
<p>You can find more information about FreshClam with the commands:</p>
<p>Unix/Linux:</p>
<pre><code class="language-bash">freshclam --help
</code></pre>
<p>Or (Unix/Linux only):</p>
<pre><code class="language-bash">man freshclam
</code></pre>
<blockquote>
<p><em>Tip</em>: Newer versions of FreshClam will create your database directory if it doesn't already exist. Older versions won't, and may fail unless you create it first.</p>
</blockquote>
<blockquote>
<p><em>Important</em>: It is common on Ubuntu after a fresh install to see the following error the first time you use ClamAV:</p>
<pre><code class="language-bash">freshclam

freshclam: error while loading shared libraries: libclamav.so.7: cannot open shared object   file: No such file or directory
</code></pre>
<p>You can fix this error by using <code>ldconfig</code> to rebuild the library search path.</p>
<pre><code class="language-bash">sudo ldconfig
</code></pre>
</blockquote>
<p>If you are having issues updating the signature databases with <code>freshclam</code>, please review <a href="../../faq/faq-freshclam.html">the <code>freshclam</code> FAQ</a>.</p>
<h2 id="sigtool"><a class="header" href="#sigtool">SigTool</a></h2>
<p>ClamAV provides <code>sigtool</code> 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 <em>libclamav</em>'s virus signatures is a false positive.</p>
<p>This can be accomplished by using the command:</p>
<pre><code class="language-bash">sigtool --unpack=FILE
</code></pre>
<p>Where FILE points to your virus signature databases. Then, once <code>sigtool</code> 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 <a href="Scanning.html#clamscan"><code>clamscan</code></a> scan reports or <a href="Scanning.html#clamd"><code>clamd</code></a> logs). As an example:</p>
<pre><code class="language-bash">grep "Win.Test.EICAR" ./*
</code></pre>
<p>Or, do all that in one step with:</p>
<pre><code class="language-bash">sigtool --find="Win.Test.EICAR"
</code></pre>
<p>This should give you the offending signature(s) in question, which can then be included as part of your <a href="https://www.clamav.net/reports/fp">false positive report</a>.</p>
<p>To learn more in depth information on how <code>sigtool</code> 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.</p>
<p>Otherwise, information on available sigtool functions can be easily referenced with:</p>
<pre><code class="language-bash">sigtool --help
</code></pre>
<p>Or (Unix/Linux only):</p>
<pre><code class="language-bash">man sigtool
</code></pre>
<h2 id="clambc"><a class="header" href="#clambc">ClamBC</a></h2>
<p><code>clambc</code> 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.</p>
<p>For more detailed help, please use:</p>
<pre><code class="language-bash">clambc --help
</code></pre>
<p>Or (Unix/Linux only):</p>
<pre><code class="language-bash">man clambc
</code></pre>
<h2 id="next-steps"><a class="header" href="#next-steps">Next Steps</a></h2>
<p>Now that you know more about FreshClam and tools to work with the signature databases, it's time to <a href="Scanning.html">run your first scan</a>.</p>
<h2 id="create-your-own-signatures"><a class="header" href="#create-your-own-signatures">Create your own signatures</a></h2>
<p>There is a whole community of malware researchers and signature writers. If you'd like to learn how to <a href="../Signatures.html">craft your own signatures</a>, you can!</p>

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