clamd.conf(5) Clam AntiVirus clamd.conf(5)

clamd.conf - Configuration file for Clam AntiVirus Daemon

clamd.conf configures the Clam AntiVirus daemon, clamd(8).

The file consists of comments and options with arguments. Each line which starts with a hash (#) symbol is ignored by the parser. Options and arguments are case sensitive and of the form Option Argument. The arguments are of the following types:

Boolean value (yes/no or true/false or 1/0).
String without blank characters.
Size in bytes. You can use 'M' or 'm' modifiers for megabytes and 'K' or 'k' for kilobytes. To specify the size in bytes just don't use modifiers.
Unsigned integer.

When some option is not used (commented out or not included in the configuration file at all) clamd takes a default action.

If this option is set clamd will not run.
Save all reports to a log file.
Default: disabled
By default the log file is locked for writing and only a single daemon process can write to it. This option disables the lock.
Default: no
Maximum size of the log file.
Value of 0 disables the limit.
Default: 1048576
Log time for each message.
Default: no
Log all clean files.
Useful in debugging but drastically increases the log size.
Default: no
Use the system logger (can work together with LogFile).
Default: no
Type of syslog messages
Please refer to 'man syslog' for facility names.
Default: LOG_LOCAL6
Enable verbose logging.
Default: no
Rotate log file. Requires LogFileMaxSize option set prior to this option.
Default: no
Log additional information about the infected file, such as its size and hash, together with the virus name.
Default: no
Save the process identifier of a listening daemon (main thread) to a specified file.
Default: disabled
This option allows you to change the default temporary directory.
Default: system specific (usually /tmp or /var/tmp).
This option allows you to change the default database directory. If you enable it, please make sure it points to the same directory in both clamd and freshclam.
Default: defined at configuration (/usr/local/share/clamav)
Only load the official signatures published by the ClamAV project.
Default: no
Path to a local (Unix) socket the daemon will listen on.
Default: disabled
Sets the group ownership on the unix socket.
Default: the primary group of the user running clamd
Sets the permissions on the unix socket to the specified mode.
Default: socket is world readable and writable
Remove stale socket after unclean shutdown.
Default: yes
TCP port number the daemon will listen on.
Default: disabled
By default clamd binds to INADDR_ANY.
This option allows you to restrict the TCP address and provide some degree of protection from the outside world. This option can be specified multiple times in order to listen on multiple IPs. IPv6 is now supported.
Default: disabled
Maximum length the queue of pending connections may grow to.
Default: 200
Close the STREAM session when the data size limit is exceeded.
The value should match your MTA's limit for the maximum attachment size.
Default: 25M
The STREAM command uses an FTP-like protocol.
This option sets the lower boundary for the port range.
Default: 1024
This option sets the upper boundary for the port range.
Default: 2048
Maximum number of threads running at the same time.
Default: 10
This option specifies the time (in seconds) after which clamd should timeout if a client doesn't provide any data.
Default: 120
This option specifies the time (in seconds) after which clamd should timeout if a client doesn't provide any initial command after connecting. The default is set to 30 to avoid timeouts with TCP sockets when processing large messages. If using a Unix socket, the value can be changed to 5. Note: the timeout for subsequents commands, and/or data chunks is specified by ReadTimeout.
Default: 30
This option specifies how long to wait (in milliseconds) if the send buffer is full. Keep this value low to prevent clamd hanging.
Default: 500
Maximum number of queued items (including those being processed by MaxThreads threads). It is recommended to have this value at least twice MaxThreads if possible.
WARNING: you shouldn't increase this too much to avoid running out of file descriptors, the following condition should hold: MaxThreads*MaxRecursion + MaxQueue - MaxThreads + 6 < RLIMIT_NOFILE. RLIMIT_NOFILE is the maximum number of open file descriptors (usually 1024), set by ulimit -n.
Default: 100
This option specifies how long (in seconds) the process should wait for a new job.
Default: 30
Don't scan files and directories matching REGEX. This directive can be used multiple times.
Default: disabled
Maximum depth directories are scanned at.
Default: 15
Follow directory symlinks.
Default: no
Scan files and directories on other filesystems.
Default: yes
Follow regular file symlinks.
Default: no
This option specifies the time intervals (in seconds) in which clamd should perform a database check.
Default: 600
Enable non-blocking (multi-threaded/concurrent) database reloads. This feature will temporarily load a second scanning engine while scanning continues using the first engine. Once loaded, the new engine takes over. The old engine is removed as soon as all scans using the old engine have completed. This feature requires more RAM, so this option is provided in case users are willing to block scans during reload in exchange for lower RAM requirements.
Default: yes
Execute a command when a virus is found. In the command string %v will be replaced with the virus name and %f will be replaced with the file name. Additionally, two environment variables will be defined: $CLAM_VIRUSEVENT_FILENAME and $CLAM_VIRUSEVENT_VIRUSNAME.
Default: disabled
Stop daemon when libclamav reports out of memory condition.
Default: no
Permit use of the ALLMATCHSCAN command.
Default: yes
Don't fork into background.
Default: no
Enable debug messages from libclamav.
Default: no
Do not remove temporary files (for debugging purpose).
Default: no
Run the daemon as a specified user (the process must be started by root).
Default: disabled
With this option enabled ClamAV will load bytecode from the database. It is highly recommended you keep this option turned on, otherwise you may miss detections for many new viruses.
Default: yes
Set bytecode security level.

Possible values:
TrustSigned - trust bytecode loaded from signed .c[lv]d files and insert runtime safety checks for bytecode loaded from other sources,
Paranoid - don't trust any bytecode, insert runtime checks for all.

Recommended: TrustSigned, because bytecode in .cvd files already has these checks.
Default: TrustSigned
Set bytecode timeout in milliseconds.
Default: 5000
Allow loading bytecode from outside digitally signed .c[lv]d files. **Caution**: You should NEVER run bytecode signatures from untrusted sources. Doing so may result in arbitrary code execution.
Default: no
Set bytecode execution mode.

Possible values:
Auto - automatically choose JIT if possible, fallback to interpreter
ForceJIT - always choose JIT, fail if not possible
ForceInterpreter - always choose interpreter
Test - run with both JIT and interpreter and compare results. Make all failures fatal.

Default: Auto
Detect Possibly Unwanted Applications.
Default: No
Exclude a specific PUA category. This directive can be used multiple times. See https://docs.clamav.net/faq/faq-pua.html for the complete list of PUA categories.
Default: disabled
Only include a specific PUA category. This directive can be used multiple times. See https://docs.clamav.net/faq/faq-pua.html for the complete list of PUA categories.
Default: disabled
In some cases (eg. complex malware, exploits in graphic files, and others), ClamAV uses special algorithms to provide accurate detection. This option controls the algorithmic detection.
Default: yes
Allow heuristic match to take precedence. When enabled, if a heuristic scan (such as phishingScan) detects a possible virus/phishing it will stop scanning immediately. Recommended, saves CPU scan-time. When disabled, virus/phishing detected by heuristic scans will be reported only at the end of a scan. If an archive contains both a heuristically detected virus/phishing, and a real malware, the real malware will be reported. Keep this disabled if you intend to handle "*.Heuristics.*" viruses differently from "real" malware. If a non-heuristically-detected virus (signature-based) is found first, the scan is interrupted immediately, regardless of this config option.
Default: no
PE stands for Portable Executable - it's an executable file format used in all 32 and 64-bit versions of Windows operating systems. This option allows ClamAV to perform a deeper analysis of executable files and it's also required for decompression of popular executable packers such as UPX.
If you turn off this option, the original files will still be scanned, but without additional processing.
Default: yes
Executable and Linking Format is a standard format for UN*X executables. This option allows you to control the scanning of ELF files.
If you turn off this option, the original files will still be scanned, but without additional processing.
Default: yes
Enable scanning of mail files.
If you turn off this option, the original files will still be scanned, but without parsing individual messages/attachments.
Default: yes
Scan RFC1341 messages split over many emails. You will need to periodically clean up $TemporaryDirectory/clamav-partial directory. WARNING: This option may open your system to a DoS attack. Never use it on loaded servers.
Default: no
Enable email signature-based phishing detection.
Default: yes
Enable URL signature-based phishing detection (Heuristics.Phishing.Email.*)
Default: yes
Enable the DLP module.
Default: no
This option sets the lowest number of Credit Card numbers found in a file to generate a detect.
Default: 3
With this option enabled the DLP module will search for valid Credit Card0umbers only. Debit and Private Label cards will not be searched.
Default: No
This option sets the lowest number of Social Security Numbers found in a file to generate a detect.
Default: 3
With this option enabled the DLP module will search for valid SSNs formatted as xxx-yy-zzzz.
Default: Yes
With this option enabled the DLP module will search for valid SSNs formatted as xxxyyzzzz.
Default: No
Perform HTML/JavaScript/ScriptEncoder normalisation and decryption.
If you turn off this option, the original files will still be scanned, but without additional processing.
Default: yes
This option enables scanning of OLE2 files, such as Microsoft Office documents and .msi files.
If you turn off this option, the original files will still be scanned, but without additional processing.
Default: yes
This option enables scanning within PDF files.
If you turn off this option, the original files will still be scanned, but without additional processing.
Default: yes
This option enables scanning within SWF files.
If you turn off this option, the original files will still be scanned, but without decoding and additional processing.
Default: yes
This option enables scanning xml-based document files supported by libclamav.
If you turn off this option, the original files will still be scanned, but without additional processing.
Default: yes
This option enables scanning HWP3 files.
If you turn off this option, the original files will still be scanned, but without additional processing.
Default: yes
Scan within archives and compressed files.
If you turn off this option, the original files will still be scanned, but without unpacking and additional processing.
Default: yes
Alert on broken executable files (PE & ELF).
Default: no
Alert on broken graphics files (JPEG, TIFF, PNG, GIF).
Default: no
Alert on encrypted archives and documents (encrypted .zip, .7zip, .rar, .pdf).
Default: no
Alert on encrypted archives (encrypted .zip, .7zip, .rar).
Default: no
Alert on encrypted documents (encrypted .pdf).
Default: no
Alert on OLE2 files containing VBA macros (Heuristics.OLE2.ContainsMacros).
Default: no
When AlertExceedsMax is set, files exceeding the MaxFileSize, MaxScanSize, or MaxRecursion limit will be flagged with the virus name starting with "Heuristics.Limits.Exceeded".
Default: no
Alert on emails containing SSL mismatches in URLs (might lead to false positives!).
Default: no
Alert on emails containing cloaked URLs (might lead to some false positives).
Default: no
Alert on raw DMG image files containing partition intersections.
Default: no
This option causes memory or nested map scans to dump the content to disk.
If you turn on this option, more data is written to disk and is available when the leave-temps option is enabled at the cost of more disk writes.
Default: no
This option sets the maximum amount of time a scan may take to complete. The value is in milliseconds. The value of 0 disables the limit. WARNING: disabling this limit or setting it too high may result allow scanning of certain files to lock up the scanning process/threads resulting in a Denial of Service.
Default: 12000
Sets the maximum amount of data to be scanned for each input file. Archives and other containers are recursively extracted and scanned up to this value. The size of an archive plus the sum of the sizes of all files within archive count toward the scan size. For example, a 1M uncompressed archive containing a single 1M inner file counts as 2M toward the max scan size. Warning: disabling this limit or setting it too high may result in severe damage to the system.
Default: 100M
Files larger than this limit won't be scanned. Affects the input file itself as well as files contained inside it (when the input file is an archive, a document or some other kind of container). Warning: disabling this limit or setting it too high may result in severe damage to the system. Technical design limitations prevent ClamAV from scanning files greater than 2 GB at this time.
Default: 25M
Nested archives are scanned recursively, e.g. if a Zip archive contains a RAR file, all files within it will also be scanned. This options specifies how deeply the process should be continued. Warning: setting this limit too high may result in severe damage to the system.
Default: 17
Number of files to be scanned within an archive, a document, or any other kind of container. Warning: disabling this limit or setting it too high may result in severe damage to the system.
Default: 10000
This option sets the maximum size of a file to check for embedded PE.
Files larger than this value will skip the additional analysis step.
Negative values are not allowed.
Default: 10M
This option sets the maximum size of a HTML file to normalize.
HTML files larger than this value will not be normalized or scanned.
Negative values are not allowed.
Default: 10M
This option sets the maximum size of a normalized HTML file to scan.
HTML files larger than this value after normalization will not be scanned.
Negative values are not allowed.
Default: 2M
This option sets the maximum size of a script file to normalize.
Script content larger than this value will not be normalized or scanned.
Negative values are not allowed.
Default: 5M
This option sets the maximum size of a ZIP file to reanalyze type recognition.
ZIP files larger than this value will skip the step to potentially reanalyze as PE.
Negative values are not allowed.
WARNING: setting this limit too high may result in severe damage or impact performance.
Default: 1M
This option sets the maximum number of partitions of a raw disk image to be scanned.
Raw disk images with more partitions than this value will have up to the value partitions scanned.
Negative values are not allowed.
WARNING: setting this limit too high may result in severe damage or impact performance.
Default: 50
This option sets the maximum number of icons within a PE to be scanned.
PE files with more icons than this value will have up to the value number icons scanned.
Negative values are not allowed.
WARNING: setting this limit too high may result in severe damage or impact performance.
Default: 100
This option sets the maximum recursive calls to HWP3 parsing function.
HWP3 files using more than this limit will be terminated and alert the user.
Scans will be unable to scan any HWP3 attachments if the recursive limit is reached.
Negative values are not allowed.
WARNING: setting this limit too high may result in severe damage or impact performance.
Default: 16
This option sets the maximum calls to the PCRE match function during an instance of regex matching.
Instances using more than this limit will be terminated and alert the user but the scan will continue.
For more information on match_limit, see the PCRE documentation.
Negative values are not allowed.
WARNING: setting this limit too high may severely impact performance.
Default: 10000
This option sets the maximum recursive calls to the PCRE match function during an instance of regex matching.
Instances using more than this limit will be terminated and alert the user but the scan will continue.
For more information on match_limit_recursion, see the PCRE documentation.
Negative values are not allowed and values > PCREMatchLimit are superfluous.
WARNING: setting this limit too high may severely impact performance.
Default: 2000
This option sets the maximum filesize for which PCRE subsigs will be executed.
Files exceeding this limit will not have PCRE subsigs executed unless a subsig is encompassed to a smaller buffer.
Negative values are not allowed.
Setting this value to zero disables the limit.
WARNING: setting this limit too high or disabling it may severely impact performance.
Default: 25M
This option specifies a directory (including all files and directories inside it), which should be scanned on access. This option can be used multiple times.
Default: disabled
This option allows excluding directories from on-access scanning. It can be used multiple times.
Default: disabled
With this option you can exclude the root UID (0). Processes run under root will be able to access all files without triggering scans or permission denied events.
Note that if clamd cannot check the uid of the process that generated an on-access scan event (e.g., because OnAccessPrevention was not enabled, and the process already exited), clamd will perform a scan. Thus, setting OnAccessExcludeRootUID is not guaranteed to prevent every access by the root user from triggering a scan (unless OnAccessPrevention is enabled).
Default: no
With this option you can exclude specific UIDs. Processes with these UIDs will be able to access all files without triggering scans or permission denied events.
This option can be used multiple times (one per line).
Note: using a value of 0 on any line will disable this option entirely. To exclude the root UID (0) please enable the OnAccessExcludeRootUID option.
Also note that if clamd cannot check the uid of the process that generated an on-access scan event (e.g., because OnAccessPrevention was not enabled, and the process already exited), clamd will perform a scan. Thus, setting OnAccessExcludeUID is not guaranteed to prevent every access by the specified uid from triggering a scan (unless OnAccessPrevention is enabled).
Default: disabled
This option allows exclusions via user names when using the on-access scanning client. It can be used multiple times, and has the same potential race condition limitations of the OnAccessExcludeUID option.
Default: disabled
Files larger than this value will not be scanned in on access.
Default: 5M
Max number of scanning threads to allocate to the OnAccess thread pool at startup. These threads are the ones responsible for creating a connection with the daemon and kicking off scanning after an event has been processed. To prevent clamonacc from consuming all clamd's resources keep this lower than clamd's max threads.
Default: 5
Max amount of time (in milliseconds) that the OnAccess client should spend for every connect, send, and recieve attempt when communicating with clamd via curl.
Default: 5000 (5 seconds)
Specifies a mount point (including all files and directories under it), which should be scanned on access. This option can be used multiple times.
Default: disabled
Disables the dynamic directory determination system which allows for recursively watching include paths.
Default: no
Enables fanotify blocking when malicious files are found.
Default: disabled
Number of times the OnAccess client will retry a failed scan due to connection problems (or other issues).
Default: 0
When using prevention, if this option is turned on, any errors that occur during scanning will result in the event attempt being denied. This could potentially lead to unwanted system behaviour with certain configurations, so the client defaults this to off and prefers allowing access events in case of scan or connection error.
Default: no
Toggles extra scanning and notifications when a file or directory is created or moved.
Requires the DDD system to kick-off extra scans.
Default: no
Disable authenticode certificate chain verification in PE files.
Default: no

All options expressing a size are limited to max 4GB. Values in excess will be reset to the maximum.

/etc/clamav/clamd.conf

Tomasz Kojm <tkojm@clamav.net>, Kevin Lin <klin@sourcefire.com>

clamd(8), clamdscan(1), clamav-milter(8), freshclam(1), freshclam.conf(5)

December 4, 2013 ClamAV 0.104.1