# Scanning

Tip: The commands on Windows are generally the same, but you may need to add the .exe extension to run the ClamAV applications.

## Daemon

### ClamD

clamd is a multi-threaded daemon that uses libclamav to scan files for viruses. Scanning behavior can be fully configured to fit most needs by modifying clamd.conf.

As clamd requires a virus signature database to run, we recommend setting up ClamAV's official signatures before running clamd using freshclam.

The daemon works by listening for commands on the sockets specified in clamd.conf. Listening is supported over both unix local sockets and TCP sockets.

IMPORTANT: clamd does not currently protect or authenticate traffic coming over the TCP socket, meaning it will accept any and all of the following commands listed from any source. Thus, we strongly recommend following best networking practices when setting up your clamd instance. I.e. don't expose your TCP socket to the Internet.

Here is a quick list of the commands accepted by clamd over the socket.

• PING
• VERSION
• RELOAD
• SHUTDOWN
• SCAN file/directory
• RAWSCAN file/directory
• CONTSCAN file/directory
• MULTISCAN file/directory
• ALLMATCHSCAN file/directory
• INSTREAM
• FILDES
• STATS
• IDSESSION, END

As with most ClamAV tools, you can find out more about these by invoking the command:

man clamd


The daemon also handles the following signals as so:

• SIGTERM - perform a clean exit
• SIGHUP - reopen the log file
• SIGUSR2 - reload the database

It should be noted that clamd should not be started using the shell operator & or other external tools which would start it as a background process. Instead, you should run clamd which will load the database and then daemonize itself (unless you have specified otherwise in clamd.conf). After that, clamd is ready to accept connections and perform file scanning.

Once you have set up your configuration to your liking, and understand how you will be sending commands to the daemon, running clamd itself is simple. Simply execute the command:

clamd


### ClamDScan

clamdscan is a clamd client, which greatly simplifies the task of scanning files with clamd. It sends commands to the clamd daemon across the socket specified in clamd.conf and generates a scan report after all requested scanning has been completed by the daemon.

Thus, to run clamdscan, you must have an instance of clamd already running as well.

Please keep in mind, that as a simple scanning client, clamdscan cannot change scanning and engine configurations. These are tied to the clamd instance and the configuration you set up in clamd.conf. Therefore, while clamdscan will accept many of the same commands as its sister tool clamscan, it will simply ignore most of them as (by design) no mechanism exists to make ClamAV engine configuration changes over the clamd socket.

Again, running clamdscan, once you have a working clamd instance, is simple:

clamdscan [*options*] [*file/directory/-*]


### ClamDTop

clamdtop is a tool to monitor one or multiple instances of clamd. It has a colorized ncurses interface, which shows each job queued, memory usage, and information about the loaded signature database for the connected clamd instance(s). By default it will attempt to connect to the local clamd as defined in clamd.conf. However, you can specify other clamd instances at the command line.

man clamdtop


or

clamdtop --help


### On-Access Scanning

The ClamOnAcc application provides On-Access Scanning for Linux systems. On-Access Scanning is a form of real-time protection that uses ClamD to scan files when they're accessed.

#### ClamOnAcc (v0.102+)

ClamAV's On-Access Scanning (clamonacc) is a client that runs in its own application alongside, but separately from the clamd instance. The On-Access Scanner is capable of preventing access to/from any malicious files it discovers--based on the verdict it receives from clamd--but by default it is configured to run in notify-only mode, which means it will simply alert the user if a malicious file is detected, then take any additional actions that the user may have specified at the command line, but it will not actively prevent processes from reading or writing to that file.

Disclaimer: Enabling Prevention mode will seriously impact performance if used on commonly accessed directories.

Tip: You can run ClamOnAcc multiple times simultaneously, each with a different config. If you want to enable Prevention-mode for one directory, while sticking to notify-only mode for any other monitored directories, that's an option!

On-Access Scanning is primarily set up through clamd.conf. However, you can learn more about all the configuration and command line options available to you by reading the On-Access Scanning User Guide.

Once you have set up the On-Access Scanner (and clamd) to your liking, you will first need to run clamd before you can start it. If your clamd instance is local, it is required you run clamd as a user that is excluded (via OnAccessExcludeUname or OnAccessExcludeUID) from On-Access scanning events (e.g.) to prevent clamonacc from triggering events endlessly as it sends scan requests to clamd:

su - clamav -c "/usr/local/bin/clamd


After the daemon is running, you can start the On-Access Scanner. clamonacc must be run as root in order to utilize its kernel event detection and intervention features:

sudo clamonacc


It will run a number of startup checks to test for a sane configuration, and ensure it can connect to clamd, and if everything checks out clamonacc will automatically fork to the background and begin monitoring your system for events.

### ClamD (v0.101)

In older versions, ClamAV's On-Access Scanner is a thread that runs within a clamd instance. The On-Access Scanner is capable of blocking access to/from any malicious files it discovers--based on the verdict it finds using the engine it shares with clamd--but by default it is configured to run in notify-only mode, which means it will simply alert the user if a malicious file is detected, but it will not actively prevent processes from reading or writing to that file.

On-Access Scanning is primarily set up through clamd.conf. However, you can learn more about all the configuration and command line options available to you by reading the On-Access Scanning User Guide.

Once you have set up the On-Access Scanner to your liking, you will need to run clamd with elevated permissions to start it.

sudo clamd


## One-Time Scanning

### ClamScan

clamscan is a command line tool which uses libclamav to scan files and/or directories for viruses. Unlike clamdscan, clamscan does not require a running clamd instance to function. Instead, clamscan will create a new engine and load in the virus database each time it is run. It will then scan the files and/or directories specified at the command line, create a scan report, and exit.

By default, when loading databases, clamscan will check the location to which freshclam installed the virus database signatures. This behavior, along with a myriad of other scanning and engine controls, can be modified by providing flags and other options at the command line.

There are too many options to list all of them here. So we'll only cover a few common and more interesting ones:

• --log=FILE - save scan report to FILE
• --database=FILE/DIR - load virus database from FILE or load all supported db files from DIR
• --official-db-only[=yes/no(*)] - only load official signatures
• --max-filesize=#n - files larger than this will be skipped and assumed clean
• --max-scansize=#n - the maximum amount of data to scan for each container file
• --leave-temps[=yes/no(*)]- do not remove temporary files
• --file-list=FILE - scan files from FILE
• --quiet - only output error messages
• --bell - sound bell on virus detection
• --cross-fs[=yes(*)/no] - scan files and directories on other filesystems
• --move=DIRECTORY - move infected files into DIRECTORY
• --copy=DIRECTORY - copy infected files into DIRECTORY
• --bytecode-timeout=N - set bytecode timeout (in milliseconds)
• --heuristic-alerts[=yes(*)/no] - toggles heuristic alerts
• --alert-encrypted[=yes/no(*)] - alert on encrypted archives and documents
• --nocerts - disable authenticode certificate chain verification in PE files
• --disable-cache - disable caching and cache checks for hash sums of scanned files

To learn more about the options available when using clamscan please reference:

man clamscan


and

clamscan --help


Otherwise, the general usage of clamscan is:

clamscan [options] [file/directory/-]


#### Some basic scans

Run this to scan the files in the current directory:

clamscan .


This will scan the current directory. At the end of the scan, it will display a summary. If you notice in the clamscan output, it only scanned something like 60 files, even though there are more files in subdirectories. By default, clamscan will only scan files in the current directory.

Run this to scan all the files in the current directory:

clamscan --recursive .


Run this to scan ALL the files on your system, it will take quite a while. Keep in mind that you can cancel it at any time by pressing Ctrl-C:

Linux/Unix:

clamscan --recursive /


Windows:

clamscan.exe --recursive C:\


## Process Memory Scanning

Note: This feature requires Windows and ClamAV version 0.105 or newer. You must also be running ClamAV as Administrator.

clamscan and clamdscan are able to scan the virtual memory of currently executing processes. To do so, use the --memory option:

clamscan --memory


The --kill and --unload options allow for killing/unloading infected loaded modules.

## Disclaimers

Disclaimer: ClamAV doesn't have a "quick scan" mode. ClamAV is malware detection toolkit, not an endpoint security suite. It's up to you to decide what to scan. A full system scan is going to take a long time with ClamAV or with any anti-virus software.

Disclaimer 2: ClamScan, ClamOnAcc, and ClamDScan each include --remove options for deleting any file which alerts during a scan. This is generally a terrible idea, unless you're monitoring an upload/downloads directory. False positives happen! You do not want to have the wrong file accidentally deleted. Instead, consider using --move or perhaps just --copy and set up script with the ClamD VirusEvent feature to notify you when something has been detected.

## Windows-specific Issues

### Globbing

Since the Windows command prompt doesn't take care of wildcard expansion, minimal emulation of unix glob() is performed internally. It supports * and ? only.

### File paths

Please always use the backslash as the path separator. SMB Network shares and UNC paths are supported.

#### Socket and libclamav API Input

The Windows version of ClamAV requires all the input to be UTF-8 encoded.

This affects:

• The API, notably the cl_scanfile() function
• ClamD socket input, e.g. the commands SCAN, CONTSCAN, MUTLISCAN, etc.
• ClamD socket output, i.e replies to the above queries

For legacy reasons ANSI (i.e. CP_ACP) input will still be accepted and processed as before, but with two important remarks:

1. Socket replies to ANSI queries will still be UTF-8 encoded.
2. ANSI sequences which are also valid UTF-8 sequences will be handled as UTF-8.

As a side note, console output (stdin and stderr) will always be OEM encoded, even when redirected to a file.