Difference between revisions of "ClamAV"

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(Set up clamav-unofficial-sigs: clamav-freshclam and not clamav-daemon should be enabled for DB updates)
(Starting the daemon: simplify, use Template:Note)
(5 intermediate revisions by the same user not shown)
Line 20: Line 20:
  
 
== Updating database ==
 
== Updating database ==
 +
 
Update the virus definitions with:
 
Update the virus definitions with:
 +
 
  # freshclam
 
  # freshclam
  
 
The database files are saved in:
 
The database files are saved in:
 +
 
  /var/lib/clamav/daily.cvd
 
  /var/lib/clamav/daily.cvd
 
  /var/lib/clamav/main.cvd
 
  /var/lib/clamav/main.cvd
 
  /var/lib/clamav/bytecode.cvd
 
  /var/lib/clamav/bytecode.cvd
  
The virus definition updater service is called {{ic|clamav-freshclam.service}}. Consider starting it and enabling it to start at boot so that the virus definitions are kept recent.
+
[[Start/enable]] {{ic|clamav-freshclam.service}} so that the virus definitions are kept recent.
  
 
== Starting the daemon ==
 
== Starting the daemon ==
  
Consider updating the database before starting the service for the first time or you will run into troubles/errors which will prevent ClamAV to start correctly.
+
{{Note|You will need to run {{ic|freshclam}} before starting the service for the first time or you will run into troubles/errors which will prevent ClamAV to start correctly.}}
  
The service is called {{ic|clamav-daemon.service}}. [[Start]] it or [[enable]] it to start at boot. You will need to run {{ic|freshclam}} prior to starting the service.
+
The service is called {{ic|clamav-daemon.service}}. [[Start]] it and [[enable]] it to start at boot.
  
 
== Testing the software ==
 
== Testing the software ==
Line 63: Line 66:
 
  user_configuration_complete="yes"
 
  user_configuration_complete="yes"
  
Enable the {{ic|clamav-unofficial-sigs}} timer:
+
[[Enable]] the {{ic|clamav-unofficial-sigs.timer}}.
 
 
# systemctl --now enable clamav-unofficial-sigs.timer
 
  
 
If you prefer a cron job instead of timer then run this instead:
 
If you prefer a cron job instead of timer then run this instead:
Line 79: Line 80:
 
To stop the cron job from running, delete this file: {{ic|/etc/cron.d/clamav-unofficial-sigs}}.
 
To stop the cron job from running, delete this file: {{ic|/etc/cron.d/clamav-unofficial-sigs}}.
  
Note that you still must have the {{ic|clamav-freshclam}} service running in order to have signature updates from ClamAV mirrors.
+
Note that you still must have the {{ic|clamav-freshclam.service}} [[started]] in order to have signature updates from ClamAV mirrors.
  
 
==== MalwarePatrol database ====
 
==== MalwarePatrol database ====
Line 113: Line 114:
 
Copy {{ic|/etc/clamav/clamav-milter.conf.sample}} to {{ic|/etc/clamav/clamav-milter.conf}} and adjust it to your needs. For example:
 
Copy {{ic|/etc/clamav/clamav-milter.conf.sample}} to {{ic|/etc/clamav/clamav-milter.conf}} and adjust it to your needs. For example:
 
   
 
   
{{hc|/etc/clamav/clamav-milter.conf|2=<nowiki>
+
{{hc|/etc/clamav/clamav-milter.conf|2=
 
MilterSocket /run/clamav/clamav-milter.sock
 
MilterSocket /run/clamav/clamav-milter.sock
 
MilterSocketMode 660
 
MilterSocketMode 660
Line 123: Line 124:
 
LogSyslog yes
 
LogSyslog yes
 
LogInfected Basic
 
LogInfected Basic
</nowiki>}}
+
}}
  
 
Create {{ic|/etc/systemd/system/clamav-milter.service}}:
 
Create {{ic|/etc/systemd/system/clamav-milter.service}}:
  
{{hc|/etc/systemd/system/clamav-milter.service|2=<nowiki>
+
{{hc|/etc/systemd/system/clamav-milter.service|2=
 
[Unit]
 
[Unit]
 
Description='ClamAV Milter'
 
Description='ClamAV Milter'
After=clamd.service
+
After=clamav-daemon.service
  
 
[Service]
 
[Service]
Line 138: Line 139:
 
[Install]
 
[Install]
 
WantedBy=multi-user.target
 
WantedBy=multi-user.target
</nowiki>}}
+
}}
  
Enable and start the service.
+
[[Enable]] and [[start]] {{ic|clamav-milter.service}}.
  
 
== OnAccessScan ==
 
== OnAccessScan ==
 +
 
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.
 
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.
  $ cat /proc/config.gz | gunzip | grep FANOTIFY=y
+
 
 +
  $ zgrep FANOTIFY /proc/config.gz
  
 
On-access scanning will scan the file while reading, writing or executing it.
 
On-access scanning will scan the file while reading, writing or executing it.
Line 151: Line 154:
  
 
{{hc|/etc/clamav/clamd.conf|
 
{{hc|/etc/clamav/clamd.conf|
# Enables on-access scan, requires clamd service running
+
# Enables on-access scan, requires clamav-daemon.service running
 
ScanOnAccess true
 
ScanOnAccess true
  
Line 171: Line 174:
 
# Specify an action to perform when clamav detects a malicious file
 
# Specify an action to perform when clamav detects a malicious file
 
# it is possible to specify an inline command too
 
# it is possible to specify an inline command too
VirusEvent /etc/clamav/detected.zsh
+
VirusEvent /etc/clamav/detected.sh
  
 
# WARNING: clamd should run as root
 
# WARNING: clamd should run as root
Line 212: Line 215:
 
  # aa-complain clamd
 
  # aa-complain clamd
  
Restart/start the service with {{ic|systemctl restart clamd.service}}.
+
[[Restart]] the {{ic|clamav-daemon.service}}.
  
 
Source: http://blog.clamav.net/2016/03/configuring-on-access-scanning-in-clamav.html
 
Source: http://blog.clamav.net/2016/03/configuring-on-access-scanning-in-clamav.html
Line 221: Line 224:
  
 
If you get the following messages after running freshclam:
 
If you get the following messages after running freshclam:
 +
 
{{bc|
 
{{bc|
 
WARNING: Clamd was NOT notified: Cannot connect to clamd through  
 
WARNING: Clamd was NOT notified: Cannot connect to clamd through  
Line 227: Line 231:
  
 
Add a sock file for ClamAV:
 
Add a sock file for ClamAV:
{{bc|
+
 
# touch /var/lib/clamav/clamd.sock
+
# touch /var/lib/clamav/clamd.sock
# chown clamav:clamav /var/lib/clamav/clamd.sock
+
# chown clamav:clamav /var/lib/clamav/clamd.sock
}}
+
 
 
Then, edit {{Ic|/etc/clamav/clamd.conf}} - uncomment this line:
 
Then, edit {{Ic|/etc/clamav/clamd.conf}} - uncomment this line:
 +
 
  LocalSocket /var/lib/clamav/clamd.sock
 
  LocalSocket /var/lib/clamav/clamd.sock
Save the file and [[Daemons|restart the daemon]] with {{ic|systemctl restart clamd.service}}.
+
 
 +
Save the file and [[restart]] {{ic|clamav-daemon.service}}.
  
 
=== Error: No supported database files found ===
 
=== Error: No supported database files found ===
  
 
If you get the next error when starting the daemon:
 
If you get the next error when starting the daemon:
 +
 
{{bc|
 
{{bc|
 
LibClamAV Error: cli_loaddb(): No supported database files found
 
LibClamAV Error: cli_loaddb(): No supported database files found
Line 243: Line 250:
 
}}
 
}}
 
   
 
   
This happens because of mismatch between {{ic|/etc/freshclam.conf}} setting {{ic|DatabaseDirectory}} and {{ic|/etc/clamd.conf}} setting {{ic|DatabaseDirectory}}.
+
This happens because of mismatch between {{ic|/etc/clamav/freshclam.conf}} setting {{ic|DatabaseDirectory}} and {{ic|/etc/clamav/clamd.conf}} setting {{ic|DatabaseDirectory}}.
{{ic|/etc/freshclam.conf}} pointing to {{ic|/var/lib/clamav}}, but {{ic|/etc/clamd.conf}} (default directory) pointing to {{ic|/usr/share/clamav}}, or other directory. Edit in {{ic|/etc/clamd.conf}} and replace with the same DatabaseDirectory like in {{ic|/etc/freshclam.conf}}. After that clamav will start up succesfully.
+
{{ic|/etc/clamav/freshclam.conf}} pointing to {{ic|/var/lib/clamav}}, but {{ic|/etc/clamav/clamd.conf}} (default directory) pointing to {{ic|/usr/share/clamav}}, or other directory. Edit in {{ic|/etc/clamav/clamd.conf}} and replace with the same DatabaseDirectory like in {{ic|/etc/clamav/freshclam.conf}}. After that clamav will start up succesfully.
  
 
=== Error: Can't create temporary directory ===
 
=== Error: Can't create temporary directory ===
  
 
If you get the following error, along with a 'HINT' containing a UID and a GID number:
 
If you get the following error, along with a 'HINT' containing a UID and a GID number:
 +
 
  # can't create temporary directory
 
  # can't create temporary directory
  
 
Correct permissions:
 
Correct permissions:
 +
 
  # chown UID:GID /var/lib/clamav & chmod 755 /var/lib/clamav
 
  # chown UID:GID /var/lib/clamav & chmod 755 /var/lib/clamav
  

Revision as of 09:11, 12 May 2018

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. Also you can install:

  • clamtk , a GUI frontend for clamav.
  • addons
    • clamtk-gnomeAUR , a simple plugin for ClamTk to allow a right-click, context menu scan of files or folders in the Nautilus file manager.
    • thunar-sendto-clamtkAUR , a simple plugin to allow a right-click, context menu scan of files or folders in Thunar.

Updating database

Update the virus definitions with:

# freshclam

The database files are saved in:

/var/lib/clamav/daily.cvd
/var/lib/clamav/main.cvd
/var/lib/clamav/bytecode.cvd

Start/enable clamav-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 troubles/errors which will prevent ClamAV to start correctly.

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.

$ curl https://www.eicar.org/download/eicar.com.txt | clamscan -

The output must include:

stdin: Eicar-Test-Signature FOUND

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 clamav-unofficial-sigsAUR and configure it in /etc/clamav-unofficial-sigs/user.conf.

This will add signatures/databases from e.g. MalwarePatrol, SecuriteInfo, Yara, Linux Malware Detect, etc. For the full list of databases, see the description of the GitHub repository.

Set up clamav-unofficial-sigs

First, edit the configuration in /etc/clamav-unofficial-sigs/user.conf, and change the following line:

# Uncomment the following line to enable the script
user_configuration_complete="yes"

Enable the clamav-unofficial-sigs.timer.

If you prefer a cron job instead of timer then run this instead:

# clamav-unofficial-sigs.sh --install-cron

This will regularly refresh the signatures from the databases used in the clamav-unofficial-sigs script and extra ones as configured in each configuration file in the /etc/clamav-unofficial-sigs folder.

To refresh signatures from these databases manually, run the following:

# clamav-unofficial-sigs.sh

To stop the cron job from running, delete this file: /etc/cron.d/clamav-unofficial-sigs.

Note that you still must have the clamav-freshclam.service started in order to have signature updates from ClamAV mirrors.

MalwarePatrol database

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

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

malwarepatrol_receipt_code="YOUR-RECEIPT-NUMBER" # enter your receipt number here
malwarepatrol_product_code="8" # Use 8 if you have a Free account or 15 if you are a Premium customer.
malwarepatrol_list="clamav_basic" # clamav_basic or clamav_ext
malwarepatrol_free="yes" # Set to yes if you have a Free account or no if you are a Premium customer.

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

Scan for viruses

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

$ clamscan myfile
$ clamscan --recursive --infected /home # or -r -i
$ clamscan --recursive --infected --exclude-dir='^/sys|^/dev' /

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 milter

Milter will scan your sendmail server for email containing virus. Copy /etc/clamav/clamav-milter.conf.sample to /etc/clamav/clamav-milter.conf and adjust it to your needs. For example:

/etc/clamav/clamav-milter.conf
MilterSocket /run/clamav/clamav-milter.sock
MilterSocketMode 660
FixStaleSocket yes
User clamav
PidFile /run/clamav/clamav-milter.pid
TemporaryDirectory /tmp
ClamdSocket unix:/var/lib/clamav/clamd.sock
LogSyslog yes
LogInfected Basic

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

/etc/systemd/system/clamav-milter.service
[Unit]
Description='ClamAV Milter'
After=clamav-daemon.service

[Service]
Type=forking
ExecStart=/usr/bin/clamav-milter --config-file /etc/clamav/clamav-milter.conf

[Install]
WantedBy=multi-user.target

Enable and start clamav-milter.service.

OnAccessScan

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.

$ zgrep FANOTIFY /proc/config.gz

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):

/etc/clamav/clamd.conf
# Enables on-access scan, requires clamav-daemon.service running
ScanOnAccess true

# Set the mount point where to recursively perform the scan,
# this could be every path or multiple path (one line for path)
OnAccessMountPath /usr
OnAccessMountPath /home/
OnAccessExcludePath /var/log/

# Flag fanotify to block any events on monitored files to perform the scan
OnAccessPrevention false

# Perform scans on newly created, moved, or renamed files
OnAccessExtraScanning true

# Check the UID from the event of fanotify
OnAccessExcludeUID 0

# Specify an action to perform when clamav detects a malicious file
# it is possible to specify an inline command too
VirusEvent /etc/clamav/detected.sh

# WARNING: clamd should run as root
User root

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:

/etc/clamav/detected.sh
#!/bin/bash
PATH=/usr/bin

alert="Signature detected: $CLAM_VIRUSEVENT_VIRUSNAME in $CLAM_VIRUSEVENT_FILENAME"

# Send the alert to systemd logger if exist, othewise to /var/log
if [[ -z $(command -v systemd-cat) ]]; then
	echo "$(date) - $alert" >> /var/log/clamav/infected.log
else
	# as "emerg", this could cause your DE to show a visual alert. Happen in Plasma. but the next visual alert is much nicer
	echo "$alert" | /usr/bin/systemd-cat -t clamav -p emerg
fi

#send an alrt to all graphical user
XUSERS=($(who|awk '{print $1$NF}'|sort -u))

for XUSER in $XUSERS; do
    NAME=(${XUSER/(/ })
    DISPLAY=${NAME[1]/)/}
    DBUS_ADDRESS=unix:path=/run/user/$(id -u ${NAME[0]})/bus
    echo "run $NAME - $DISPLAY - $DBUS_ADDRESS -" >> /tmp/testlog 
    /usr/bin/sudo -u ${NAME[0]} DISPLAY=${DISPLAY} \
                       DBUS_SESSION_BUS_ADDRESS=${DBUS_ADDRESS} \
                       PATH=${PATH} \
                       /usr/bin/notify-send -i dialog-warning "clamAV" "$alert"
done

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

# aa-complain clamd

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:

WARNING: Clamd was NOT notified: Cannot connect to clamd through 
/var/lib/clamav/clamd.sock connect(): No such file or directory

Add a sock file for ClamAV:

# touch /var/lib/clamav/clamd.sock
# chown clamav:clamav /var/lib/clamav/clamd.sock

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

LocalSocket /var/lib/clamav/clamd.sock

Save the file and restart clamav-daemon.service.

Error: No supported database files found

If you get the next error when starting the daemon:

LibClamAV Error: cli_loaddb(): No supported database files found
in /var/lib/clamav ERROR: Not supported data format

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 succesfully.

Error: Can't create temporary directory

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

# can't create temporary directory

Correct permissions:

# chown UID:GID /var/lib/clamav & chmod 755 /var/lib/clamav

See also