clamav/docs/man/clamd.conf.5.in

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.TH "clamd.conf" "5" "December 4, 2013" "ClamAV @VERSION@" "Clam AntiVirus"
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.SH "NAME"
.LP
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\fBclamd.conf\fR \- Configuration file for Clam AntiVirus Daemon
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.SH "DESCRIPTION"
.LP
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clamd.conf configures the Clam AntiVirus daemon, clamd(8).
.SH "FILE FORMAT"
The file consists of comments and options with arguments. Each line which starts with a hash (\fB#\fR) symbol is ignored by the parser. Options and arguments are case sensitive and of the form \fBOption Argument\fR. The arguments are of the following types:
.TP
\fBBOOL\fR
Boolean value (yes/no or true/false or 1/0).
.TP
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\fBSTRING\fR
String without blank characters.
.TP
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\fBSIZE\fR
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.
.TP
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\fBNUMBER\fR
Unsigned integer.
.SH "DIRECTIVES"
.LP
When some option is not used (commented out or not included in the configuration file at all) clamd takes a default action.
.TP
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\fBExample\fR
If this option is set clamd will not run.
.TP
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\fBLogFile STRING\fR
Save all reports to a log file.
.br
Default: disabled
.TP
\fBLogFileUnlock BOOL\fR
By default the log file is locked for writing and only a single daemon process can write to it. This option disables the lock.
.br
Default: no
.TP
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\fBLogFileMaxSize SIZE\fR
Maximum size of the log file.
.br
Value of 0 disables the limit.
.br
Default: 1048576
.TP
\fBLogTime BOOL\fR
Log time for each message.
.br
Default: no
.TP
\fBLogClean BOOL\fR
Log all clean files.
.br
Useful in debugging but drastically increases the log size.
.br
Default: no
.TP
\fBLogSyslog BOOL\fR
Use the system logger (can work together with LogFile).
.br
Default: no
.TP
\fBLogFacility STRING\fR
Type of syslog messages
.br
Please refer to 'man syslog' for facility names.
.br
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Default: LOG_LOCAL6
.TP
\fBLogVerbose BOOL\fR
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Enable verbose logging.
.br
Default: no
.TP
\fBLogRotate BOOL\fR
Rotate log file. Requires LogFileMaxSize option set prior to this option.
.br
Default: no
.TP
\fBExtendedDetectionInfo BOOL\fR
Log additional information about the infected file, such as its size and hash, together with the virus name.
.br
Default: no
.TP
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\fBPidFile STRING\fR
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Save the process identifier of a listening daemon (main thread) to a specified file.
.br
Default: disabled
.TP
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\fBTemporaryDirectory STRING\fR
This option allows you to change the default temporary directory.
.br
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Default: system specific (usually /tmp or /var/tmp).
.TP
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\fBDatabaseDirectory STRING\fR
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.
.br
Default: defined at configuration (/usr/local/share/clamav)
.TP
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\fBOfficialDatabaseOnly BOOL\fR
Only load the official signatures published by the ClamAV project.
.br
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Default: no
.TP
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\fBLocalSocket STRING\fR
Path to a local (Unix) socket the daemon will listen on.
.br
Default: disabled
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.TP
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\fBLocalSocketGroup STRING\fR
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Sets the group ownership on the unix socket.
.br
Default: the primary group of the user running clamd
.TP
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\fBLocalSocketMode STRING\fR
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Sets the permissions on the unix socket to the specified mode.
.br
Default: socket is world readable and writable
.TP
\fBFixStaleSocket BOOL\fR
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Remove stale socket after unclean shutdown.
.br
Default: yes
.TP
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\fBTCPSocket NUMBER\fR
TCP port number the daemon will listen on.
.br
Default: disabled
.TP
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\fBTCPAddr STRING\fR
By default clamd binds to INADDR_ANY.
.br
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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.
.br
Default: disabled
.TP
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\fBMaxConnectionQueueLength NUMBER\fR
Maximum length the queue of pending connections may grow to.
.br
Default: 200
.TP
\fBStreamMaxLength SIZE\fR
Close the STREAM session when the data size limit is exceeded.
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.br
The value should match your MTA's limit for the maximum attachment size.
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.br
Default: 25M
.TP
\fBStreamMinPort NUMBER\fR
The STREAM command uses an FTP-like protocol.
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.br
This option sets the lower boundary for the port range.
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.br
Default: 1024
.TP
\fBStreamMaxPort NUMBER\fR
This option sets the upper boundary for the port range.
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.br
Default: 2048
.TP
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\fBMaxThreads NUMBER\fR
Maximum number of threads running at the same time.
.br
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Default: 10
.TP
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\fBReadTimeout NUMBER\fR
This option specifies the time (in seconds) after which clamd should
timeout if a client doesn't provide any data.
.br
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Default: 120
.TP
\fBCommandReadTimeout NUMBER\fR
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.
.br
Default: 30
.TP
\fBSendBufTimeout NUMBER\fR
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This option specifies how long to wait (in milliseconds) if the send buffer is full.
Keep this value low to prevent clamd hanging.
.br
Default: 500
.TP
\fBMaxQueue NUMBER\fR
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.
.br
\fBWARNING: 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.\fR
RLIMIT_NOFILE is the maximum number of open file descriptors (usually 1024), set
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by \fBulimit \-n\fR.
.br
Default: 100
.TP
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\fBIdleTimeout NUMBER\fR
This option specifies how long (in seconds) the process should wait
for a new job.
.br
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Default: 30
.TP
\fBExcludePath REGEX\fR
Don't scan files and directories matching REGEX. This directive can be used multiple times.
.br
Default: disabled
.TP
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\fBMaxDirectoryRecursion NUMBER\fR
Maximum depth directories are scanned at.
.br
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Default: 15
.TP
\fBFollowDirectorySymlinks BOOL\fR
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Follow directory symlinks.
.br
Default: no
.TP
\fBCrossFilesystems BOOL\fR
Scan files and directories on other filesystems.
.br
Default: yes
.TP
\fBFollowFileSymlinks BOOL\fR
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Follow regular file symlinks.
.br
Default: no
.TP
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\fBSelfCheck NUMBER\fR
This option specifies the time intervals (in seconds) in which clamd
should perform a database check.
.br
Default: 600
.TP
\fBConcurrentDatabaseReload BOOL\fR
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.
.br
Default: yes
.TP
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\fBVirusEvent COMMAND\fR
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.
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\fR
.br
Default: disabled
.TP
\fBExitOnOOM BOOL\fR
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Stop daemon when libclamav reports out of memory condition.
.br
Default: no
.TP
\fBAllowAllMatchScan BOOL\fR
Permit use of the ALLMATCHSCAN command.
.br
Default: yes
.TP
\fBForeground BOOL\fR
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Don't fork into background.
.br
Default: no
.TP
\fBDebug BOOL\fR
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Enable debug messages from libclamav.
.br
Default: no
.TP
\fBLeaveTemporaryFiles BOOL\fR
Do not remove temporary files (for debugging purpose).
.br
Default: no
.TP
\fBGenerateMetadataJson BOOL\fR
Record metadata about the file being scanned.
Scan metadata is useful for file analysis purposes and for debugging scan behavior.
The JSON metadata will be printed after the scan is complete if Debug is enabled.
A metadata.json file will be written to the scan temp directory if LeaveTemporaryFiles is enabled.
.br
Default: no
.TP
\fBUser STRING\fR
Run the daemon as a specified user (the process must be started by root).
.br
Default: disabled
.TP
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\fBBytecode BOOL\fR
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.
.br
Default: yes
.TP
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\fBBytecodeSecurity STRING\fR
Set bytecode security level.
.RS
.PD 0
.HP 4
Possible values:
.br
\fBTrustSigned\fR \- trust bytecode loaded from signed .c[lv]d files and insert runtime safety checks for bytecode loaded from other sources,
.br
\fBParanoid\fR \- don't trust any bytecode, insert runtime checks for all.
.RE
.RS
Recommended: \fBTrustSigned\fR, because bytecode in .cvd files already has these checks.
.br
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Default: TrustSigned
.PD 1
.RE
.TP
\fBBytecodeTimeout NUMBER\fR
Set bytecode timeout in milliseconds.
.br
Default: 5000
.TP
\fBBytecodeUnsigned BOOL\fR
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.
.br
Default: no
.TP
\fBBytecodeMode STRING\fR
Set bytecode execution mode.
.RS
.PD 0
.HP 4
Possible values:
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.br
\fBAuto\fR \- automatically choose JIT if possible, fallback to interpreter
.br
\fBForceJIT\fR \- always choose JIT, fail if not possible
.br
\fBForceInterpreter\fR \- always choose interpreter
.br
\fBTest\fR \- run with both JIT and interpreter and compare results. Make all failures fatal.
.RE
.RS
Default: Auto
.PD 1
.RE
.TP
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\fBDetectPUA BOOL\fR
Detect Possibly Unwanted Applications.
.br
Default: No
.TP
\fBExcludePUA CATEGORY\fR
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.
.br
Default: disabled
.TP
\fBIncludePUA CATEGORY\fR
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.
.br
Default: disabled
.TP
\fBHeuristicAlerts BOOL\fR
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.
.br
Default: yes
.TP
\fBHeuristicScanPrecedence BOOL\fR
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.
.br
Default: no
.TP
\fBScanPE BOOL\fR
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.
.br
If you turn off this option, the original files will still be scanned, but without additional processing.
.br
Default: yes
.TP
\fBScanELF BOOL\fR
Executable and Linking Format is a standard format for UN*X executables. This option allows you to control the scanning of ELF files.
.br
If you turn off this option, the original files will still be scanned, but without additional processing.
.br
Default: yes
.TP
\fBScanMail BOOL\fR
Enable scanning of mail files.
.br
If you turn off this option, the original files will still be scanned, but without parsing individual messages/attachments.
.br
Default: yes
.TP
\fBScanPartialMessages BOOL\fR
Scan RFC1341 messages split over many emails. You will need to periodically clean up $TemporaryDirectory/clamav-partial directory. \fBWARNING: This option may open your system to a DoS attack. Never use it on loaded servers.\fR
.br
Default: no
.TP
\fBPhishingSignatures BOOL\fR
Enable email signature-based phishing detection.
.br
Default: yes
.TP
\fBPhishingScanURLs BOOL\fR
Enable URL signature-based phishing detection (Heuristics.Phishing.Email.*)
.br
Default: yes
.TP
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\fBStructuredDataDetection BOOL\fR
Enable the DLP module.
.br
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Default: no
.TP
\fBStructuredMinCreditCardCount NUMBER\fR
This option sets the lowest number of Credit Card numbers found in a file to generate a detect.
.br
Default: 3
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.TP
\fBStructuredCCOnly BOOL\fR
With this option enabled the DLP module will search for valid Credit Card\nnumbers only. Debit and Private Label cards will not be searched.
.br
Default: No
.TP
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\fBStructuredMinSSNCount NUMBER\fR
This option sets the lowest number of Social Security Numbers found in a file to generate a detect.
.br
Default: 3
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.TP
\fBStructuredSSNFormatNormal BOOL\fR
With this option enabled the DLP module will search for valid SSNs formatted as xxx-yy-zzzz.
.br
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Default: Yes
.TP
\fBStructuredSSNFormatStripped BOOL\fR
With this option enabled the DLP module will search for valid SSNs formatted as xxxyyzzzz.
.br
Default: No
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.TP
\fBScanHTML BOOL\fR
Perform HTML/JavaScript/ScriptEncoder normalisation and decryption.
.br
If you turn off this option, the original files will still be scanned, but without additional processing.
.br
Default: yes
.TP
\fBScanOLE2 BOOL\fR
This option enables scanning of OLE2 files, such as Microsoft Office documents and .msi files.
.br
If you turn off this option, the original files will still be scanned, but without additional processing.
.br
Default: yes
.TP
\fBScanPDF BOOL\fR
This option enables scanning within PDF files.
.br
If you turn off this option, the original files will still be scanned, but without additional processing.
.br
Default: yes
.TP
\fBScanSWF BOOL\fR
This option enables scanning within SWF files.
.br
If you turn off this option, the original files will still be scanned, but without decoding and additional processing.
.br
Default: yes
.TP
\fBScanXMLDOCS BOOL\fR
This option enables scanning xml-based document files supported by libclamav.
.br
If you turn off this option, the original files will still be scanned, but without additional processing.
.br
Default: yes
.TP
\fBScanHWP3 BOOL\fR
This option enables scanning HWP3 files.
.br
If you turn off this option, the original files will still be scanned, but without additional processing.
.br
Default: yes
.TP
\fBScanArchive BOOL\fR
Scan within archives and compressed files.
.br
If you turn off this option, the original files will still be scanned, but without unpacking and additional processing.
.br
Default: yes
.TP
\fBAlertBrokenExecutables BOOL\fR
Alert on broken executable files (PE & ELF).
.br
Default: no
.TP
GIF, PNG bugfixes; Add AlertBrokenMedia option Added a new scan option to alert on broken media (graphics) file formats. This feature mitigates the risk of malformed media files intended to exploit vulnerabilities in other software. At present media validation exists for JPEG, TIFF, PNG, and GIF files. To enable this feature, set `AlertBrokenMedia yes` in clamd.conf, or use the `--alert-broken-media` option when using `clamscan`. These options are disabled by default for now. Application developers may enable this scan option by enabling `CL_SCAN_HEURISTIC_BROKEN_MEDIA` for the `heuristic` scan option bit field. Fixed PNG parser logic bugs that caused an excess of parsing errors and fixed a stack exhaustion issue affecting some systems when scanning PNG files. PNG file type detection was disabled via signature database update for 0.103.0 to mitigate effects from these bugs. Fixed an issue where PNG and GIF files no longer work with Target:5 (graphics) signatures if detected as CL_TYPE_PNG/GIF rather than as CL_TYPE_GRAPHICS. Target types now support up to 10 possible file types to make way for additional graphics types in future releases. Scanning JPEG, TIFF, PNG, and GIF files will no longer return "parse" errors when file format validation fails. Instead, the scan will alert with the "Heuristics.Broken.Media" signature prefix and a descriptive suffix to indicate the issue, provided that the "alert broken media" feature is enabled. GIF format validation will no longer fail if the GIF image is missing the trailer byte, as this appears to be a relatively common issue in otherwise functional GIF files. Added a TIFF dynamic configuration (DCONF) option, which was missing. This will allow us to disable TIFF format validation via signature database update in the event that it proves to be problematic. This feature already exists for many other file types. Added CL_TYPE_JPEG and CL_TYPE_TIFF types.
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\fBAlertBrokenMedia BOOL\fR
Alert on broken graphics files (JPEG, TIFF, PNG, GIF).
.br
Default: no
.TP
\fBAlertEncrypted BOOL\fR
Alert on encrypted archives and documents (encrypted .zip, .7zip, .rar, .pdf).
.br
Default: no
.TP
\fBAlertEncryptedArchive BOOL\fR
Alert on encrypted archives (encrypted .zip, .7zip, .rar).
.br
Default: no
.TP
\fBAlertEncryptedDoc BOOL\fR
Alert on encrypted documents (encrypted .pdf).
.br
Default: no
.TP
\fBAlertOLE2Macros BOOL\fR
Alert on OLE2 files containing VBA macros (Heuristics.OLE2.ContainsMacros).
.br
Default: no
.TP
\fBAlertExceedsMax BOOL\fR
When AlertExceedsMax is set, files exceeding the MaxFileSize, MaxScanSize, or MaxRecursion limit will be flagged with the virus name starting with "Heuristics.Limits.Exceeded".
.br
Default: no
.TP
\fBAlertPhishingSSLMismatch BOOL\fR
Alert on emails containing SSL mismatches in URLs (might lead to false positives!).
.br
Default: no
.TP
\fBAlertPhishingCloak BOOL\fR
Alert on emails containing cloaked URLs (might lead to some false positives).
.br
Default: no
.TP
\fBAlertPartitionIntersection BOOL\fR
Alert on raw DMG image files containing partition intersections.
.br
Default: no
.TP
\fBForceToDisk\fR
This option causes memory or nested map scans to dump the content to disk.
.br
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.
.br
Default: no
.TP
\fBMaxScanTime SIZE\fR
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. \fBWARNING: 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.\fR
.br
Default: 120000
.TP
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\fBMaxScanSize SIZE\fR
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. \fBWarning: disabling this limit or setting it too high may result in severe damage to the system.\fR
.br
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Default: 100M
.TP
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\fBMaxFileSize SIZE\fR
Fix errors when scanning files > 4G This commit resolves https://bugzilla.clamav.net/show_bug.cgi?id=12673 Changes in 0.103 to order of operations for creating fmaps and performaing hashes of fmaps resulted errors when scanning files that are 4096M and a different (but related) error when scanning files > 4096M. This is despite the fact that scanning is supposed to be limited to --max-scansize (MaxScanSize) and was also apparently limited to INT_MAX - 2 (aka ~1.999999G) back in 2014 to alleviate reported crashes for a few large file formats. (see https://bugzilla.clamav.net/show_bug.cgi?id=10960) This last limitation was not documented, so I added it to the sample clamd.conf. Anyways, the main issue is that the fmap module was using "unsigned int" and was then enforcing a limitation (verbose error messages) when that a map length exceeded the capapacity of an unsigned int. This commit switches the associated variables over to uint64_t, and while fmaps are still limited to size_t in other places, the fmap module will at least work with files > 4G on 64bit systems. In testing this, I found that the time to hash a file, particularly when hashing a file on an NTFS partition from Linux was really slow because we were hashing in FILEBUFF chunks (about 8K) at a time. Increasing this to 10MB chunks speeds up scanning of large files. Finally, now that hashing is performed immediately when an fmap is created for a file, hashing of files larger than max-scansize was occuring. This commit adds checks to bail out early if the file size exceeds the maximum before creating an fmap. It will alert with the Heuristics.Limits.Exceeded name if the heuristic is enabled. Also fixed CheckFmapFeatures.cmake module that detects if sysconf(_SC_PAGESIZE) is available.
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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). \fBWarning: 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.\fR
.br
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Default: 25M
.TP
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\fBMaxRecursion NUMBER\fR
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. \fBWarning: setting this limit too high may result in severe damage to the system.\fR
.br
libclamav: Fix scan recursion tracking Scan recursion is the process of identifying files embedded in other files and then scanning them, recursively. Internally this process is more complex than it may sound because a file may have multiple layers of types before finding a new "file". At present we treat the recursion count in the scanning context as an index into both our fmap list AND our container list. These two lists are conceptually a part of the same thing and should be unified. But what's concerning is that the "recursion level" isn't actually incremented or decremented at the same time that we add a layer to the fmap or container lists but instead is more touchy-feely, increasing when we find a new "file". To account for this shadiness, the size of the fmap and container lists has always been a little longer than our "max scan recursion" limit so we don't accidentally overflow the fmap or container arrays (!). I've implemented a single recursion-stack as an array, similar to before, which includes a pointer to each fmap at each layer, along with the size and type. Push and pop functions add and remove layers whenever a new fmap is added. A boolean argument when pushing indicates if the new layer represents a new buffer or new file (descriptor). A new buffer will reset the "nested fmap level" (described below). This commit also provides a solution for an issue where we detect embedded files more than once during scan recursion. For illustration, imagine a tarball named foo.tar.gz with this structure: | description | type | rec level | nested fmap level | | ------------------------- | ----- | --------- | ----------------- | | foo.tar.gz | GZ | 0 | 0 | | └── foo.tar | TAR | 1 | 0 | | ├── bar.zip | ZIP | 2 | 1 | | │   └── hola.txt | ASCII | 3 | 0 | | └── baz.exe | PE | 2 | 1 | But suppose baz.exe embeds a ZIP archive and a 7Z archive, like this: | description | type | rec level | nested fmap level | | ------------------------- | ----- | --------- | ----------------- | | baz.exe | PE | 0 | 0 | | ├── sfx.zip | ZIP | 1 | 1 | | │   └── hello.txt | ASCII | 2 | 0 | | └── sfx.7z | 7Z | 1 | 1 | |    └── world.txt | ASCII | 2 | 0 | (A) If we scan for embedded files at any layer, we may detect: | description | type | rec level | nested fmap level | | ------------------------- | ----- | --------- | ----------------- | | foo.tar.gz | GZ | 0 | 0 | | ├── foo.tar | TAR | 1 | 0 | | │ ├── bar.zip | ZIP | 2 | 1 | | │ │   └── hola.txt | ASCII | 3 | 0 | | │ ├── baz.exe | PE | 2 | 1 | | │ │ ├── sfx.zip | ZIP | 3 | 1 | | │ │ │   └── hello.txt | ASCII | 4 | 0 | | │ │ └── sfx.7z | 7Z | 3 | 1 | | │ │    └── world.txt | ASCII | 4 | 0 | | │ ├── sfx.zip | ZIP | 2 | 1 | | │ │   └── hello.txt | ASCII | 3 | 0 | | │ └── sfx.7z | 7Z | 2 | 1 | | │   └── world.txt | ASCII | 3 | 0 | | ├── sfx.zip | ZIP | 1 | 1 | | └── sfx.7z | 7Z | 1 | 1 | (A) is bad because it scans content more than once. Note that for the GZ layer, it may detect the ZIP and 7Z if the signature hits on the compressed data, which it might, though extracting the ZIP and 7Z will likely fail. The reason the above doesn't happen now is that we restrict embedded type scans for a bunch of archive formats to include GZ and TAR. (B) If we scan for embedded files at the foo.tar layer, we may detect: | description | type | rec level | nested fmap level | | ------------------------- | ----- | --------- | ----------------- | | foo.tar.gz | GZ | 0 | 0 | | └── foo.tar | TAR | 1 | 0 | | ├── bar.zip | ZIP | 2 | 1 | | │   └── hola.txt | ASCII | 3 | 0 | | ├── baz.exe | PE | 2 | 1 | | ├── sfx.zip | ZIP | 2 | 1 | | │   └── hello.txt | ASCII | 3 | 0 | | └── sfx.7z | 7Z | 2 | 1 | |    └── world.txt | ASCII | 3 | 0 | (B) is almost right. But we can achieve it easily enough only scanning for embedded content in the current fmap when the "nested fmap level" is 0. The upside is that it should safely detect all embedded content, even if it may think the sfz.zip and sfx.7z are in foo.tar instead of in baz.exe. The biggest risk I can think of affects ZIPs. SFXZIP detection is identical to ZIP detection, which is why we don't allow SFXZIP to be detected if insize of a ZIP. If we only allow embedded type scanning at fmap-layer 0 in each buffer, this will fail to detect the embedded ZIP if the bar.exe was not compressed in foo.zip and if non-compressed files extracted from ZIPs aren't extracted as new buffers: | description | type | rec level | nested fmap level | | ------------------------- | ----- | --------- | ----------------- | | foo.zip | ZIP | 0 | 0 | | └── bar.exe | PE | 1 | 1 | | └── sfx.zip | ZIP | 2 | 2 | Provided that we ensure all files extracted from zips are scanned in new buffers, option (B) should be safe. (C) If we scan for embedded files at the baz.exe layer, we may detect: | description | type | rec level | nested fmap level | | ------------------------- | ----- | --------- | ----------------- | | foo.tar.gz | GZ | 0 | 0 | | └── foo.tar | TAR | 1 | 0 | | ├── bar.zip | ZIP | 2 | 1 | | │   └── hola.txt | ASCII | 3 | 0 | | └── baz.exe | PE | 2 | 1 | | ├── sfx.zip | ZIP | 3 | 1 | | │   └── hello.txt | ASCII | 4 | 0 | | └── sfx.7z | 7Z | 3 | 1 | |    └── world.txt | ASCII | 4 | 0 | (C) is right. But it's harder to achieve. For this example we can get it by restricting 7ZSFX and ZIPSFX detection only when scanning an executable. But that may mean losing detection of archives embedded elsewhere. And we'd have to identify allowable container types for each possible embedded type, which would be very difficult. So this commit aims to solve the issue the (B)-way. Note that in all situations, we still have to scan with file typing enabled to determine if we need to reassign the current file type, such as re-identifying a Bzip2 archive as a DMG that happens to be Bzip2- compressed. Detection of DMG and a handful of other types rely on finding data partway through or near the ned of a file before reassigning the entire file as the new type. Other fixes and considerations in this commit: - The utf16 HTML parser has weak error handling, particularly with respect to creating a nested fmap for scanning the ascii decoded file. This commit cleans up the error handling and wraps the nested scan with the recursion-stack push()/pop() for correct recursion tracking. Before this commit, each container layer had a flag to indicate if the container layer is valid. We need something similar so that the cli_recursion_stack_get_*() functions ignore normalized layers. Details... Imagine an LDB signature for HTML content that specifies a ZIP container. If the signature actually alerts on the normalized HTML and you don't ignore normalized layers for the container check, it will appear as though the alert is in an HTML container rather than a ZIP container. This commit accomplishes this with a boolean you set in the scan context before scanning a new layer. Then when the new fmap is created, it will use that flag to set similar flag for the layer. The context flag is reset those that anything after this doesn't have that flag. The flag allows the new recursion_stack_get() function to ignore normalized layers when iterating the stack to return a layer at a requested index, negative or positive. Scanning normalized extracted/normalized javascript and VBA should also use the 'layer is normalized' flag. - This commit also fixes Heuristic.Broken.Executable alert for ELF files to make sure that: A) these only alert if cli_append_virus() returns CL_VIRUS (aka it respects the FP check). B) all broken-executable alerts for ELF only happen if the SCAN_HEURISTIC_BROKEN option is enabled. - This commit also cleans up the error handling in cli_magic_scan_dir(). This was needed so we could correctly apply the layer-is-normalized-flag to all VBA macros extracted to a directory when scanning the directory. - Also fix an issue where exceeding scan maximums wouldn't cause embedded file detection scans to abort. Granted we don't actually want to abort if max filesize or max recursion depth are exceeded... only if max scansize, max files, and max scantime are exceeded. Add 'abort_scan' flag to scan context, to protect against depending on correct error propagation for fatal conditions. Instead, setting this flag in the scan context should guarantee that a fatal condition deep in scan recursion isn't lost which result in more stuff being scanned instead of aborting. This shouldn't be necessary, but some status codes like CL_ETIMEOUT never used to be fatal and it's easier to do this than to verify every parser only returns CL_ETIMEOUT and other "fatal status codes" in fatal conditions. - Remove duplicate is_tar() prototype from filestypes.c and include is_tar.h instead. - Presently we create the fmap hash when creating the fmap. This wastes a bit of CPU if the hash is never needed. Now that we're creating fmap's for all embedded files discovered with file type recognition scans, this is a much more frequent occurence and really slows things down. This commit fixes the issue by only creating fmap hashes as needed. This should not only resolve the perfomance impact of creating fmap's for all embedded files, but also should improve performance in general. - Add allmatch check to the zip parser after the central-header meta match. That way we don't multiple alerts with the same match except in allmatch mode. Clean up error handling in the zip parser a tiny bit. - Fixes to ensure that the scan limits such as scansize, filesize, recursion depth, # of embedded files, and scantime are always reported if AlertExceedsMax (--alert-exceeds-max) is enabled. - Fixed an issue where non-fatal alerts for exceeding scan maximums may mask signature matches later on. I changed it so these alerts use the "possibly unwanted" alert-type and thus only alert if no other alerts were found or if all-match or heuristic-precedence are enabled. - Added the "Heuristics.Limits.Exceeded.*" events to the JSON metadata when the --gen-json feature is enabled. These will show up once under "ParseErrors" the first time a limit is exceeded. In the present implementation, only one limits-exceeded events will be added, so as to prevent a malicious or malformed sample from filling the JSON buffer with millions of events and using a tonne of RAM.
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Default: 17
.TP
2008-02-15 12:16:11 +00:00
\fBMaxFiles NUMBER\fR
Number of files to be scanned within an archive, a document, or any other kind of container. \fBWarning: disabling this limit or setting it too high may result in severe damage to the system.\fR
.br
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Default: 10000
.TP
\fBMaxEmbeddedPE SIZE\fR
This option sets the maximum size of a file to check for embedded PE.
.br
Files larger than this value will skip the additional analysis step.
.br
Negative values are not allowed.
.br
Default: 10M
.TP
\fBMaxHTMLNormalize SIZE\fR
This option sets the maximum size of a HTML file to normalize.
.br
HTML files larger than this value will not be normalized or scanned.
.br
Negative values are not allowed.
.br
Default: 10M
.TP
\fBMaxHTMLNoTags SIZE\fR
This option sets the maximum size of a normalized HTML file to scan.
.br
HTML files larger than this value after normalization will not be scanned.
.br
Negative values are not allowed.
.br
Default: 2M
.TP
\fBMaxScriptNormalize SIZE\fR
This option sets the maximum size of a script file to normalize.
.br
Script content larger than this value will not be normalized or scanned.
.br
Negative values are not allowed.
.br
Default: 5M
.TP
\fBMaxZipTypeRcg SIZE\fR
This option sets the maximum size of a ZIP file to reanalyze type recognition.
.br
ZIP files larger than this value will skip the step to potentially reanalyze as PE.
.br
Negative values are not allowed.
.br
WARNING: setting this limit too high may result in severe damage or impact performance.
.br
Default: 1M
.TP
\fBMaxPartitions SIZE\fR
This option sets the maximum number of partitions of a raw disk image to be scanned.
.br
Raw disk images with more partitions than this value will have up to the value partitions scanned.
.br
Negative values are not allowed.
.br
WARNING: setting this limit too high may result in severe damage or impact performance.
.br
Default: 50
.TP
\fBMaxIconsPE SIZE\fR
This option sets the maximum number of icons within a PE to be scanned.
.br
PE files with more icons than this value will have up to the value number icons scanned.
.br
Negative values are not allowed.
.br
WARNING: setting this limit too high may result in severe damage or impact performance.
.br
Default: 100
.TP
\fBMaxRecHWP3 NUMBER\fR
This option sets the maximum recursive calls to HWP3 parsing function.
.br
HWP3 files using more than this limit will be terminated and alert the user.
.br
Scans will be unable to scan any HWP3 attachments if the recursive limit is reached.
.br
Negative values are not allowed.
.br
WARNING: setting this limit too high may result in severe damage or impact performance.
.br
Default: 16
.TP
\fBPCREMatchLimit NUMBER\fR
This option sets the maximum calls to the PCRE match function during an instance of regex matching.
.br
Instances using more than this limit will be terminated and alert the user but the scan will continue.
.br
For more information on match_limit, see the PCRE documentation.
.br
Negative values are not allowed.
.br
WARNING: setting this limit too high may severely impact performance.
.br
Default: 10000
.TP
\fBPCRERecMatchLimit NUMBER\fR
This option sets the maximum recursive calls to the PCRE match function during an instance of regex matching.
.br
Instances using more than this limit will be terminated and alert the user but the scan will continue.
.br
For more information on match_limit_recursion, see the PCRE documentation.
.br
Negative values are not allowed and values > PCREMatchLimit are superfluous.
.br
WARNING: setting this limit too high may severely impact performance.
.br
Default: 2000
.TP
\fBPCREMaxFileSize SIZE\fR
This option sets the maximum filesize for which PCRE subsigs will be executed.
.br
Files exceeding this limit will not have PCRE subsigs executed unless a subsig is encompassed to a smaller buffer.
.br
Negative values are not allowed.
.br
Setting this value to zero disables the limit.
.br
WARNING: setting this limit too high or disabling it may severely impact performance.
.br
Default: 25M
.TP
\fBOnAccessIncludePath STRING\fR
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.
.br
Default: disabled
.TP
\fBOnAccessExcludePath STRING\fR
This option allows excluding directories from on-access scanning. It can be used multiple times.
.br
Default: disabled
.TP
\fBOnAccessExcludeRootUID BOOL\fR
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.
.br
Note that if clamd cannot check the uid of the process that generated an on-access scan event (e.g., because \fBOnAccessPrevention\fR was not enabled, and the process already exited), clamd will perform a scan. Thus, setting \fBOnAccessExcludeRootUID\fR is not \fIguaranteed\fR to prevent every access by the root user from triggering a scan (unless \fBOnAccessPrevention\fR is enabled).
.br
Default: no
.TP
\fBOnAccessExcludeUID NUMBER\fR
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.
.br
This option can be used multiple times (one per line).
.br
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.
.br
Also note that if clamd cannot check the uid of the process that generated an on-access scan event (e.g., because \fBOnAccessPrevention\fR was not enabled, and the process already exited), clamd will perform a scan. Thus, setting \fBOnAccessExcludeUID\fR is not \fIguaranteed\fR to prevent every access by the specified uid from triggering a scan (unless \fBOnAccessPrevention\fR is enabled).
.br
Default: disabled
.TP
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\fBOnAccessExcludeUname STRING\fR
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.
.br
Default: disabled
.TP
\fBOnAccessMaxFileSize SIZE\fR
Files larger than this value will not be scanned in on access.
.br
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Default: 5M
.TP
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\fBOnAccessMaxThreads NUMBER\fR
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.
.br
Default: 5
.TP
\fBOnAccessCurlTimeout NUMBER\fR
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.
.br
Default: 5000 (5 seconds)
.TP
\fBOnAccessMountPath STRING\fR
Specifies a mount point (including all files and directories under it), which should be scanned on access. This option can be used multiple times.
.br
Default: disabled
.TP
\fBOnAccessDisableDDD BOOL\fR
Disables the dynamic directory determination system which allows for recursively watching include paths.
.br
Default: no
.TP
\fBOnAccessPrevention BOOL\fR
Enables fanotify blocking when malicious files are found.
.br
Default: disabled
.TP
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\fBOnAccessRetryAttempts NUMBER\fR
Number of times the OnAccess client will retry a failed scan due to connection problems (or other issues).
.br
Default: 0
.TP
\fBOnAccessDenyOnError BOOL\fR
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.
.br
Default: no
.TP
\fBOnAccessExtraScanning BOOL\fR
Toggles extra scanning and notifications when a file or directory is created or moved.
.br
Requires the DDD system to kick-off extra scans.
.br
Default: no
.TP
\fBDisableCertCheck BOOL\fR
Disable authenticode certificate chain verification in PE files.
.br
Default: no
2009-04-03 11:09:00 +00:00
.SH "NOTES"
.LP
Spelling Adjustments (#30) * spelling: accessed * spelling: alignment * spelling: amalgamated * spelling: answers * spelling: another * spelling: acquisition * spelling: apitid * spelling: ascii * spelling: appending * spelling: appropriate * spelling: arbitrary * spelling: architecture * spelling: asynchronous * spelling: attachments * spelling: argument * spelling: authenticode * spelling: because * spelling: boundary * spelling: brackets * spelling: bytecode * spelling: calculation * spelling: cannot * spelling: changes * spelling: check * spelling: children * spelling: codegen * spelling: commands * spelling: container * spelling: concatenated * spelling: conditions * spelling: continuous * spelling: conversions * spelling: corresponding * spelling: corrupted * spelling: coverity * spelling: crafting * spelling: daemon * spelling: definition * spelling: delivered * spelling: delivery * spelling: delimit * spelling: dependencies * spelling: dependency * spelling: detection * spelling: determine * spelling: disconnects * spelling: distributed * spelling: documentation * spelling: downgraded * spelling: downloading * spelling: endianness * spelling: entities * spelling: especially * spelling: empty * spelling: expected * spelling: explicitly * spelling: existent * spelling: finished * spelling: flexibility * spelling: flexible * spelling: freshclam * spelling: functions * spelling: guarantee * spelling: hardened * spelling: headaches * spelling: heighten * spelling: improper * spelling: increment * spelling: indefinitely * spelling: independent * spelling: inaccessible * spelling: infrastructure Conflicts: docs/html/node68.html * spelling: initializing * spelling: inited * spelling: instream * spelling: installed * spelling: initialization * spelling: initialize * spelling: interface * spelling: intrinsics * spelling: interpreter * spelling: introduced * spelling: invalid * spelling: latency * spelling: lawyers * spelling: libclamav * spelling: likelihood * spelling: loop * spelling: maximum * spelling: million * spelling: milliseconds * spelling: minimum * spelling: minzhuan * spelling: multipart * spelling: misled * spelling: modifiers * spelling: notifying * spelling: objects * spelling: occurred * spelling: occurs * spelling: occurrences * spelling: optimization * spelling: original * spelling: originated * spelling: output * spelling: overridden * spelling: parenthesis * spelling: partition * spelling: performance * spelling: permission * spelling: phishing * spelling: portions * spelling: positives * spelling: preceded * spelling: properties * spelling: protocol * spelling: protos * spelling: quarantine * spelling: recursive * spelling: referring * spelling: reorder * spelling: reset * spelling: resources * spelling: resume * spelling: retrieval * spelling: rewrite * spelling: sanity * spelling: scheduled * spelling: search * spelling: section * spelling: separator * spelling: separated * spelling: specify * spelling: special * spelling: statement * spelling: streams * spelling: succession * spelling: suggests * spelling: superfluous * spelling: suspicious * spelling: synonym * spelling: temporarily * spelling: testfiles * spelling: transverse * spelling: turkish * spelling: typos * spelling: unable * spelling: unexpected * spelling: unexpectedly * spelling: unfinished * spelling: unfortunately * spelling: uninitialized * spelling: unlocking * spelling: unnecessary * spelling: unpack * spelling: unrecognized * spelling: unsupported * spelling: usable * spelling: wherever * spelling: wishlist * spelling: white * spelling: infrastructure * spelling: directories * spelling: overridden * spelling: permission * spelling: yesterday * spelling: initialization * spelling: intrinsics * space adjustment for spelling changes * minor modifications by klin
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All options expressing a size are limited to max 4GB. Values in excess will be reset to the maximum.
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.SH "FILES"
.LP
@CONFDIR@/clamd.conf
.SH "AUTHORS"
.LP
Tomasz Kojm <tkojm@clamav.net>, Kevin Lin <klin@sourcefire.com>
2004-09-26 01:28:55 +00:00
.SH "SEE ALSO"
.LP
2010-05-06 17:02:53 +02:00
clamd(8), clamdscan(1), clamav-milter(8), freshclam(1), freshclam.conf(5)