How to Scan Files for Malware & Set Content Restrictions in Node.js

It’s becoming more and more common for threat actors to launch custom-content cyberattacks — and these types of attacks can be exceedingly difficult for threat scanners to detect.

Thankfully, using the below code, we can take advantage of a free API that simultaneously scans files for malware (with both advanced heuristics & signature-based scanning) and allows us to place custom restrictions against threatening file types.

This means we can simply block file types that threat actors might use to bypass our malware scanning policies — including executables, invalid files, scripts, password protected files, and more. For even more stringent protection, we can simply provide our own comma-separated “whitelist” of file extensions in the API request body, ensuring files which don’t pass in-depth content verification against our list trigger a CleanResult: False response during the scan.

We can structure our API call in a few quick steps. Our first step is to install the SDK, which we can either do by running the following command:

npm install cloudmersive-virus-api-client --save

Or by adding the following snippet to our package.json:

  "dependencies": {
    "cloudmersive-virus-api-client": "^1.1.9"
  }

Now we can include the below code in our file. First and foremost, we’ll need a free API key to authorize our request (this allows 800 API calls per month with no commitment & can be obtained on the Cloudmersive website). Once we include that, we can go about setting custom content restriction booleans to our liking, and we can enter our comma-separated whitelist (no spaces) in the restrictFileTypes parameter.

var CloudmersiveVirusApiClient = require('cloudmersive-virus-api-client');
var defaultClient = CloudmersiveVirusApiClient.ApiClient.instance;

// Configure API key authorization: Apikey
var Apikey = defaultClient.authentications['Apikey'];
Apikey.apiKey = 'YOUR API KEY';



var apiInstance = new CloudmersiveVirusApiClient.ScanApi();

var inputFile = Buffer.from(fs.readFileSync("C:\\temp\\inputfile").buffer); // File | Input file to perform the operation on.

var opts = { 
  'allowExecutables': true, // Boolean | Set to false to block executable files (program code) from being allowed in the input file.  Default is false (recommended).
  'allowInvalidFiles': true, // Boolean | Set to false to block invalid files, such as a PDF file that is not really a valid PDF file, or a Word Document that is not a valid Word Document.  Default is false (recommended).
  'allowScripts': true, // Boolean | Set to false to block script files, such as a PHP files, Python scripts, and other malicious content or security threats that can be embedded in the file.  Set to true to allow these file types.  Default is false (recommended).
  'allowPasswordProtectedFiles': true, // Boolean | Set to false to block password protected and encrypted files, such as encrypted zip and rar files, and other files that seek to circumvent scanning through passwords.  Set to true to allow these file types.  Default is false (recommended).
  'allowMacros': true, // Boolean | Set to false to block macros and other threats embedded in document files, such as Word, Excel and PowerPoint embedded Macros, and other files that contain embedded content threats.  Set to true to allow these file types.  Default is false (recommended).
  'allowXmlExternalEntities': true, // Boolean | Set to false to block XML External Entities and other threats embedded in XML files, and other files that contain embedded content threats.  Set to true to allow these file types.  Default is false (recommended).
  'allowInsecureDeserialization': true, // Boolean | Set to false to block Insecure Deserialization and other threats embedded in JSON and other object serialization files, and other files that contain embedded content threats.  Set to true to allow these file types.  Default is false (recommended).
  'allowHtml': true, // Boolean | Set to false to block HTML input in the top level file; HTML can contain XSS, scripts, local file accesses and other threats.  Set to true to allow these file types.  Default is false (recommended) [for API keys created prior to the release of this feature default is true for backward compatability].
  'restrictFileTypes': "restrictFileTypes_example" // String | Specify a restricted set of file formats to allow as clean as a comma-separated list of file formats, such as .pdf,.docx,.png would allow only PDF, PNG and Word document files.  All files must pass content verification against this list of file formats, if they do not, then the result will be returned as CleanResult=false.  Set restrictFileTypes parameter to null or empty string to disable; default is disabled.
};

var callback = function(error, data, response) {
  if (error) {
    console.error(error);
  } else {
    console.log('API called successfully. Returned data: ' + data);
  }
};
apiInstance.scanFileAdvanced(inputFile, opts, callback);

Now we can pass files through a free, multifaceted scanning service before sharing or storing them elsewhere.