A small WordPress plugin which attempts to detect VirtualBox.

is_virtualbox.php

<?php
/**
 * Plugin Name:     VirtualBox Detection.
 * Description:     Attempt to detect VirtualBox.
 * Author:          WordPress Core Contributors
 * Author URI:      https://make.wordpress.org/core
 * License:         GPLv2 or later.
 * Version:         1.0.1
 * Gist Plugin URI: https://gist.github.com/costdev/75138bbb72f77166e05cf49b5952f821
 */

/**
 * Attempt to detect a VirtualBox environment.
 *
 * This attempts all known methods of detecting VirtualBox.
 *
 * @global $wp_filesystem The filesystem.
 *
 * @since 1.0.0
 *
 * @return bool Whether or not VirtualBox was detected.
 */
function is_virtualbox() {
	global $wp_filesystem;
	static $is_virtualbox;

	if ( $is_virtualbox ) {
		return $is_virtualbox;
	}

	// Detection via filter.
	if ( apply_filters( 'is_virtualbox', false ) ) {
		$is_virtualbox = 'Detected via filter';
		return $is_virtualbox;
	}

	// Detection via Composer.
	if ( function_exists( 'getenv' ) && getenv( 'COMPOSER_RUNTIME_ENV' ) === 'virtualbox' ) {
		$is_virtualbox = 'Detected via Composer';
		return $is_virtualbox;
	}

	$virtualbox_unames = array( 'vvv' );

	// Detection via `php_uname()`.
	if ( function_exists( 'php_uname' ) && in_array( php_uname( 'n' ), $virtualbox_unames, true ) ) {
		$is_virtualbox = 'Detected via php_uname()';
		return $is_virtualbox;
	}

	/*
	 * Vagrant can use alternative providers.
	 * This isn't reliable without some additional check(s).
	 */
	$virtualbox_usernames = array( 'vagrant' );

	// Detection via user name with POSIX.
	if ( function_exists( 'posix_getpwuid' ) && function_exists( 'posix_geteuid' ) ) {
		$user = posix_getpwuid( posix_geteuid() );

		if ( $user && in_array( $user['name'], $virtualbox_usernames, true ) ) {
			$is_virtualbox = 'Detected via posix_getpwuid( posix_geteuid() )';
			return $is_virtualbox;
		}
	}

	// Initialize the filesystem if not set.
	if ( ! $wp_filesystem ) {
		require_once ABSPATH . '/wp-admin/includes/file.php';
		WP_Filesystem();
	}

	// Detection via file owner.
	if ( in_array( $wp_filesystem->owner( __FILE__ ), $virtualbox_usernames, true ) ) {
		$is_virtualbox = 'Detected via file owner using $wp_filesystem';
		return $is_virtualbox;
	}

	// Detection via file group.
	if ( in_array( $wp_filesystem->group( __FILE__ ), $virtualbox_usernames, true ) ) {
		$is_virtualbox = 'Detected via file group using $wp_filesystem';
		return $is_virtualbox;
	}

	// Give up.
	$is_virtualbox = false;
	return $is_virtualbox;
}

add_action( 'admin_notices', 'show_whether_virtualbox' );
function show_whether_virtualbox() {
	$is_virtualbox = is_virtualbox();
	printf(
		'<div class="notice notice-info"><p>%s</p></div>',
		$is_virtualbox ? $is_virtualbox . ' - ' . __( 'This site uses VirtualBox.' ) : __( 'This site does not use VirtualBox.' )
	);
}