Contents 3 ClamAV User Manual, c 2007 - 2013 Sourcefire, Inc. Authors: Tomasz Kojm This document is distributed under the terms of the GNU General Public License v2. First of all, you have to install the ClamAV plugin (os-clamav) from the plugins view. After a page reload you will get a new menu entry under services for ClamAV.

There are a number of solutions on the market for scanning a Mac for files that have become infected with a virus or macro-virus. Many of these have a negative return on investment. So customers can instead go the open source route to scan files and quarantine them. And customers can use Jamf Pro to enable doing so. This page is meant to provide a quick and dirty guide to doing so, along with how this might be packaged and potentially tracked with Jamf Pro. First, we’ll install and configure a free tool called clamav.There are a number of ways to install clam. For this example, just to get it done quickly, we’ll use homebrew which is simply brew with the install verb and clamav as the recipe to be brewed:This is going to place your configuration files in /usr/local/etc/clamav and these cannot be used as those supplied by default are simply sample configurations. Because the .sample files have a line that indicates they are an “Example” they cannot be used. So we’ll copy the sample configuration files for freshclam.conf and clamd.conf (the demonized version) and then remove the Example line using the following two lines:Next, we’ll need to update the virus definitions for clamav. This can be run without the fully qualified file path but we are going to go ahead and include it as some computers might have another version installed (e.g. via macOS Server):The initial scan should cover the full hard drive and can be run as clamscanYour routinely run jobs should be setup to a quarantine location. Because all users should be able to see their data that was quarantined we would write this to /Users/Shared/Quarantine. We can then use a standard clamscan to scan the system and then “move” quarantined items to that location and log those transactions to /Users/Shared/Quarantine/Quarantine.txt.You can then use an Extension Attribute to read the Quarantine.txt file:Every environment is different. When combined with standard mrt scans using the built-in malware removal tool for macOS, clamAV can provide a routine added protection to isolate and help you remediate infections.Finally, it seems like I have yet to discuss antivirus and malware without getting into the conversation about whether you need it or not. In this post I am in no way taking a side on that argument, and it’s worth mentioning that I’m also not using “antivirus” to exclusively reference viruses but instead including all forms of malware. Rather, I’m exploring options for scanning systems routinely.You can easily run this nightly and parse the quarantine.txt file prior to picking it up with the Extension Attribute routinely in order to provided an additional layer of defense against potential threats to the Mac. Putting all of this into a software package would be rudimentary, and could benefit many organizations without putting our coworkers through the performance hit that many a commercial antivirus solution brings with it.Note: A special thanks to Steven Thomas Smith for pointing out that clamdscan is multi-threaded!

Clam AntiVirus is an open source (GPL) anti-virus toolkit for UNIX. It provides a number of utilities including a flexible and scalable multi-threaded daemon, a command line scanner and advanced tool for automatic database updates. Because ClamAV's main use is on file/mail servers for Windows desktops, it primarily detects Windows viruses and malware with its built-in signatures.

Installation

Install the clamav package.

Updating database

Update the virus definitions with:

If you are behind a proxy, edit /etc/clamav/freshclam.conf and update HTTPProxyServer, HTTPProxyPort, HTTPProxyUsername and HTTPProxyPassword.

The database files are saved in:

Start/enableclamav-freshclam.service so that the virus definitions are kept recent.

Starting the daemon

Note:

• You will need to run freshclam before starting the service for the first time or you will run into trouble/errors which will prevent ClamAV from starting correctly.
• The daemon is not needed if you only want to perform stand-alone scans. See Scan for viruses below.

The service is called clamav-daemon.service. Start it and enable it to start at boot.

Testing the software

In order to make sure ClamAV and the definitions are installed correctly, scan the EICAR test file (a harmless signature with no virus code) with clamscan.

The output must include:

Otherwise; read the Troubleshooting part or ask for help in the Arch Forums.

Adding more databases/signatures repositories

ClamAV can use databases/signature from other repositories or security vendors.

To add the most important ones in a single step, install either clamav-unofficial-sigs^AUR (see GitHub description) or python-fangfrisch^AUR (see online documentation). Both will add signatures/databases from popular providers, e.g. MalwarePatrol, SecuriteInfo, Yara, Linux Malware Detect, etc.

Option #1: Set up Fangfrisch

Fangfrisch was designed as a more secure, flexible and convenient replacement for clamav-unofficial-sigs, and requires very little configuration.

Most importantly, Fangfrisch never needs to be run with root permissions, unlike clamav-unofficial-sigs.

Create database structure by running:

Enable the fangfrisch.timer.

Option #2: Set up clamav-unofficial-sigs

Enable the clamav-unofficial-sigs.timer.

This will regularly update the unofficial signatures based on the configuration files in the directory /etc/clamav-unofficial-sigs.

To update signatures manually, run the following:

To change any default settings, refer and modify /etc/clamav-unofficial-sigs/user.conf.

MalwarePatrol database

If you would like to use the MalwarePatrol database, sign up for an account at https://www.malwarepatrol.net/free-guard-upgrade-option.

In /etc/clamav-unofficial-sigs/user.conf, change the following to enable this functionality:

Source: https://www.malwarepatrol.net/clamav-configuration-guide/

Scan for viruses

There are two options for on-demand scanning:

using the stand-alone scanner

clamscan can be used to scan certain files, home directories, or an entire system:

If you would like clamscan to remove the infected file add to the command the --remove option, or you can use --move=/dir to quarantine them.

You may also want clamscan to scan larger files. In this case, append the options --max-filesize=4000M and --max-scansize=4000M to the command. '4000M' is the largest possible value, and may be lowered as necessary.

Using the -l /path/to/file option will print the clamscan logs to a text file for locating reported infections.

using the daemon

clamdscan is similar to the above but utilizes the daemon, which must be running for the command to work. Most options are ignored since the daemon reads the the settings specified in /etc/clamav/clamd.conf.

Using the milter

Milter will scan your sendmail server for email containing virus.Adjust the config /etc/clamav/clamav-milter.conf to your needs. For example:

Create /etc/systemd/system/clamav-milter.service:

Enable and startclamav-milter.service.

For Postfix add the following lines to /etc/postfix/main.cf:

Check journalctl if the permission to access clamav-milter.socket for postfix is set accordingly, if not, add user postfix to group clamav.

OnAccessScan

This article or section is out of date.

On-access scanning requires the kernel to be compiled with the fanotify kernel module (kernel >= 3.8). Check if fanotify has been enabled before enabling on-access scanning.

Clamav Mac Download

On-access scanning will scan the file while reading, writing or executing it.

First, edit the /etc/clamav/clamd.conf configuration file by adding the following to the end of the file (you can also change the individual options):

Next, create the file /etc/clamav/detected.sh and add the following. This allows you to change/specify the debug message when a virus has been detected by clamd's on-access scanning service:

If you are using AppArmor, it is also necessary to allow clamd to run as root:

Restart the clamav-daemon.service.

Source: http://blog.clamav.net/2016/03/configuring-on-access-scanning-in-clamav.html

Troubleshooting

Error: Clamd was NOT notified

If you get the following messages after running freshclam:

Add a sock file for ClamAV:

Then, edit /etc/clamav/clamd.conf - uncomment this line:

Save the file and restartclamav-daemon.service.

Error: No supported database files found

If you get the next error when starting the daemon:

This happens because of mismatch between /etc/clamav/freshclam.conf setting DatabaseDirectory and /etc/clamav/clamd.conf setting DatabaseDirectory. /etc/clamav/freshclam.conf pointing to /var/lib/clamav, but /etc/clamav/clamd.conf (default directory) pointing to /usr/share/clamav, or other directory. Edit in /etc/clamav/clamd.conf and replace with the same DatabaseDirectory like in /etc/clamav/freshclam.conf. After that clamav will start up successfully.

Error: Can't create temporary directory

If you get the following error, along with a 'HINT' containing a UID and a GID number:

Correct permissions:

Tips and tricks

Run in multiple threads

Using clamscan

When scanning a file or directory from command line using clamscan only single CPU thread is used. This may be ok in cases when timing is not critical or you do not want computer to become sluggish. If there is a need to scan large folder or USB drive quickly you may want to use all available CPUs to speed up the process.

clamscan is designed to be single-threaded, so xargs can be used to run the scan in parallel:

In this example the -P parameter for xargs runs clamscan in as many processes as there are CPUs (reported by nproc at the same time. --max-lines and --max-args options will allow even finer control of batching the workload across the threads.

Using clamdscan

If you already have clamd daemon running clamdscan can be used instead (see #Starting the daemon):

Here the --multiscan parameter enables clamd to scan the contents of the directory in parallel using available threads. --fdpass parameter is required to pass the file descriptor permissions to clamd as the daemon is running under clamav user and group.

The number of available threads for clamdscan is determined in /etc/clamav/clamd.conf via MaxThreads parameter clamd.conf(5). Even though you may see that the number of MaxThreads specified is more than one (current default is 10), when you start the scan using clamdscan from command line and do not specify --multiscan option, only one effective CPU thread will be used for scanning.

Clamav Mac Os

See also

How Good Is Clamav