Stops WordPress uploading images if the filename contains certain words.

check-upload-filename.php

<?php
/*
Plugin Name: Check Upload Filename
Plugin URI: https://www.robertwent.com/
Description: Prevents image uploads by filename
Version: 1.0
Author: Robert Went
*/

add_filter('wp_handle_upload_prefilter', 'check_for_lazy_people_uploads' );

function check_for_lazy_people_uploads( $file ){

	$bad_words = array(
		'screenshot',
		'unsplash',
		'shutterstock',
		'istock',
		'img_' //Camara phones
	);

	//Check if the filename contains any matches
	$name = strtolower($file['name']);
	foreach ( $bad_words as $word ) {
		if ( stripos( $name, $word ) !== false ) {
			//Match found, so stop the upload and show an error message
			$file['error'] = __( 'Please take a couple of seconds to optimise your image filename before uploading! Filenames should not include: ' ) . $word;
		}
	}

	return $file;
}