How to Use the 'clamdscan' Command (with Examples)

The clamdscan command is a tool used within the ClamAV suite to scan files or directories for viruses using the ClamAV Daemon. This tool is designed to efficiently analyze data for potential threats with a variety of options that tailor the scanning process to specific needs. It’s widely used in both personal and server environments to maintain security by detecting malicious files. ClamAV, being an open-source project, allows users to integrate these scans into larger security systems, enhancing protection through automation and precise threat detection.

Use Case 1: Scan a File or Directory for Vulnerabilities

Code:

clamdscan path/to/file_or_directory

Motivation: Scanning specific files or directories for vulnerabilities is crucial for maintaining the integrity and security of data. This command helps in verifying whether files are infected with viruses, ensuring that the data being stored or shared is safe from threats.

Explanation:

• clamdscan: Invokes the ClamAV scanning tool using the ClamAV Daemon, which speeds up the scanning process by eliminating the need to load virus databases for each scan.
• path/to/file_or_directory: This is a placeholder for the actual path to the file or directory that you want to scan for viruses and malware.

Example Output:

/example_directory/file.txt: OK
/example_directory/infected_file.exe: TROJAN FOUND
...
----------- SCAN SUMMARY -----------
Known viruses: 6754332
Engine version: 0.103.2
Scanned directories: 1
Scanned files: 2
Infected files: 1
Data scanned: 2.34 MB
Data read: 2.00 MB (ratio 1.17:1)
Time: 4.827 sec (0 m 4 s)

Use Case 2: Scan Data from stdin

Code:

command | clamdscan -

Motivation: Sometimes, you may want to scan data that is being passed through a pipeline instead of existing as a file. This use case is essential for real-time data processing, where data streamed from one command needs to be verified before being used further down the pipeline.

Explanation:

• command: Represents any command that outputs data you wish to scan.
• |: The pipe operator passes the output of the first command as input to clamdscan.
• clamdscan: Initiates the scan of the incoming data.
• -: Tells clamdscan to read data from stdin instead of a file or directory.

Example Output:

Streaming data: OK
...
----------- SCAN SUMMARY -----------
Known viruses: 6754332
Engine version: 0.103.2
Scanned files: 1
Infected files: 0
Data scanned: 1.28 MB
Data read: 1.00 MB (ratio 1.28:1)
Time: 2.984 sec (0 m 2 s)

Use Case 3: Scan the Current Directory and Output Only Infected Files

Code:

clamdscan --infected

Motivation: When managing large sets of files, it is more efficient to focus only on infected files. By outputting only these, users can quickly ascertain which files need attention, thus improving productivity and response times to threats.

Explanation:

• clamdscan: Starts the virus scanning process.
• --infected: This option limits the output to display only the files that are infected, suppressing the list of files that are considered safe.

Example Output:

/current_directory/infected_file.exe: TROJAN FOUND
...
----------- SCAN SUMMARY -----------
Known viruses: 6754332
Engine version: 0.103.2
Scanned directories: 1
Scanned files: 2
Infected files: 1
Data scanned: 2.34 MB
Data read: 2.00 MB (ratio 1.17:1)
Time: 3.561 sec (0 m 3 s)

Use Case 4: Print the Scan Report to a Log File

Code:

clamdscan --log path/to/log_file

Motivation: Documenting scan results can be important for audit trails or reviewing scan histories. By logging scan results to a file, administrators can keep a detailed record of scanning operations, which is useful for security assessments and compliance reporting.

Explanation:

• clamdscan: Initiates the scan.
• --log: Directs output to a specified log file instead of displaying it on the console.
• path/to/log_file: Specifies the path where the log of scanning results should be saved.

Example Output (in the log file):

/example_directory/file.txt: OK
/example_directory/infected_file.exe: TROJAN FOUND
...
----------- SCAN SUMMARY -----------
Known viruses: 6754332
Engine version: 0.103.2
Scanned directories: 1
Scanned files: 2
Infected files: 1
Data scanned: 2.34 MB
Data read: 2.00 MB (ratio 1.17:1)
Time: 3.765 sec (0 m 3 s)

Use Case 5: Move Infected Files to a Specific Directory

Code:

clamdscan --move path/to/quarantine_directory

Motivation: Quarantining infected files helps prevent the spread of viruses while allowing further analysis of the threat, without deleting potentially important files. This use case is particularly useful in systems where files need to be reviewed before deletion.

Explanation:

• clamdscan: Activates the scanning operation.
• --move: This option instructs the tool to relocate infected files.
• path/to/quarantine_directory: Specifies the directory where infected files should be moved to for isolated safekeeping.

Example Output:

/example_directory/infected_file.exe: Moved
...
----------- SCAN SUMMARY -----------
Known viruses: 6754332
Engine version: 0.103.2
Scanned directories: 1
Scanned files: 2
Infected files: 1
Data scanned: 2.34 MB
Data read: 2.00 MB (ratio 1.17:1)
Time: 5.123 sec (0 m 5 s)

Use Case 6: Remove Infected Files

Code:

clamdscan --remove

Motivation: Automatically removing infected files is suitable for environments where maintaining file safety is prioritized over file review, such as in sandbox environments or automated cleanup scripts. This action helps in swiftly managing threats by eradicating them immediately.

Explanation:

• clamdscan: Runs the scanning protocol.
• --remove: Deletes any files identified as infected during the scanning process.

Example Output:

/example_directory/infected_file.exe: Removed
...
----------- SCAN SUMMARY -----------
Known viruses: 6754332
Engine version: 0.103.2
Scanned directories: 1
Scanned files: 2
Infected files: 1
Data scanned: 2.34 MB
Data read: 2.00 MB (ratio 1.17:1)
Time: 4.239 sec (0 m 4 s)

Use Case 7: Use Multiple Threads to Scan a Directory

Code:

clamdscan --multiscan

Motivation: In systems with multiple processors or cores, using multithreaded scans can significantly accelerate the detection of viruses across large datasets, enhancing efficiency and minimizing downtime during security operations.

Explanation:

• clamdscan: Initiates the virus scanning.
• --multiscan: This option enables the use of multiple threads for scanning, distributing the workload and leveraging available computing resources for faster results.

Example Output:

/example_directory/file1.txt: OK
/example_directory/file2.txt: OK
/example_directory/infected_file.exe: TROJAN FOUND
...
----------- SCAN SUMMARY -----------
Known viruses: 6754332
Engine version: 0.103.2
Scanned directories: 1
Scanned files: 3
Infected files: 1
Data scanned: 3.45 MB
Data read: 3.00 MB (ratio 1.15:1)
Time: 2.345 sec (0 m 2 s)

Use Case 8: Pass the File Descriptor Instead of Streaming the File to the Daemon

Code:

clamdscan --fdpass

Motivation: Passing file descriptors can be useful in certain environments where security policies or file system constraints might limit streaming large files. This approach can enhance performance in such scenarios by reducing the need for copies of files in memory.

Explanation:

• clamdscan: Begins the scanning process.
• --fdpass: This option passes the file descriptor to clamdscan, which can be more efficient in some situations, as it allows the daemon to access files directly.

Example Output:

/example_directory/file1.txt: OK
/example_directory/infected_file.exe: TROJAN FOUND
...
----------- SCAN SUMMARY -----------
Known viruses: 6754332
Engine version: 0.103.2
Scanned directories: 1
Scanned files: 2
Infected files: 1
Data scanned: 4.12 MB
Data read: 4.00 MB (ratio 1.03:1)
Time: 3.567 sec (0 m 3 s)

Conclusion:

clamdscan offers a suite of options that cater to a range of scanning needs, from basic virus detection to more complex tasks such as multithreaded scanning and file management post-detection. By understanding and utilizing these capabilities effectively, users can significantly enhance their system’s security, ensuring that the data remains safe and threats are dealt with swiftly and appropriately.