WordPress at a glance
function is not described

wp_authenticate_spam_check() WP 3.7.0

For Multisite blogs, check if the authenticated user has been marked as a spammer, or if the user's primary blog has been marked as spam.

Hooks in function
Return

WP_User/WP_Error. WP_User on success, WP_Error if the user is considered a spammer.

Usage

wp_authenticate_spam_check( $user );
$user(WP_User/WP_Error/null) (required)
WP_User or WP_Error object from a previous callback.
Default: null

Code of wp authenticate spam check: wp-includes/user.php WP 5.2.2

<?php
function wp_authenticate_spam_check( $user ) {
	if ( $user instanceof WP_User && is_multisite() ) {
		/**
		 * Filters whether the user has been marked as a spammer.
		 *
		 * @since 3.7.0
		 *
		 * @param bool    $spammed Whether the user is considered a spammer.
		 * @param WP_User $user    User to check against.
		 */
		$spammed = apply_filters( 'check_is_user_spammed', is_user_spammy( $user ), $user );

		if ( $spammed ) {
			return new WP_Error( 'spammer_account', __( '<strong>ERROR</strong>: Your account has been marked as a spammer.' ) );
		}
	}
	return $user;
}