diff --git a/auth.php b/auth.php
index b59420c..fa91355 100644
--- a/auth.php
+++ b/auth.php
@@ -79,9 +79,11 @@ class auth_plugin_emailotp extends auth_plugin_base {
         // OTP already generated and base credentials matches.
         if (isset($_SESSION[self::COMPONENT_NAME]) &&
                 $_SESSION[self::COMPONENT_NAME]['credentials'] === static::get_credentials($username)) {
-            return empty($password)
-                ? (bool) $this->redirect($username, notification::NOTIFY_INFO)
-                : password_verify($password, $_SESSION[self::COMPONENT_NAME]['password']);
+            if (empty($password)) {
+                return (bool) $this->redirect($username, notification::NOTIFY_INFO);
+            } else if (password_verify($password, $_SESSION[self::COMPONENT_NAME]['password'])) {
+                return true;
+            } 
         }
         // OTP request - do not proceed on preventaccountcreation when user not exits.
         if (!isset($_SESSION[self::COMPONENT_NAME]) && empty($password) && (
@@ -96,6 +98,18 @@ class auth_plugin_emailotp extends auth_plugin_base {
                 : notification::NOTIFY_ERROR
             );
         }
+        // OTP exits but validation failed - reset if revoke threshold is set.
+        if (isset($_SESSION[self::COMPONENT_NAME])) {
+            $_SESSION[self::COMPONENT_NAME]['login_failed_count']++;
+            if (!empty($this->config->revokethreshold) && 
+                    $_SESSION[self::COMPONENT_NAME]['login_failed_count'] >= $this->config->revokethreshold) {
+                unset($_SESSION[self::COMPONENT_NAME]);
+                \core\notification::add(
+                    (string)new lang_string('otpinvalidated', self::COMPONENT_NAME, null, $CFG->lang),
+                    notification::NOTIFY_WARNING
+                );
+            }
+        }
         return false;
     }
 
@@ -181,6 +195,7 @@ class auth_plugin_emailotp extends auth_plugin_base {
         $_SESSION[self::COMPONENT_NAME] = array(
             'credentials' => static::get_credentials($username),
             'password'    => password_hash($newpassword, PASSWORD_DEFAULT),
+            'login_failed_count' => 0,
         );
         $a = (object)array(
             'username' => $username,
diff --git a/lang/en/auth_emailotp.php b/lang/en/auth_emailotp.php
index c401e0c..f4476ab 100644
--- a/lang/en/auth_emailotp.php
+++ b/lang/en/auth_emailotp.php
@@ -28,6 +28,12 @@ $string['otpgeneratedtext'] = 'One-time password for current session: {$a->passw
 $string['otpsentsuccess'] = 'One-time password was sent to given email.';
 $string['otpsenterror'] = 'An error occurred while sending one-time password.';
 $string['otpsentinfo'] = 'One-time password for current session was already generated and sent to email.';
+$string['otpinvalidated'] = 'Previously generated password has been revoked due to exceeding the login failure threshold.';
+$string['optperioderror'] = 'Minim period after which another password can be generated not preserved. Try again later.';
+$string['revokethreshold'] = 'Revoke threshold';
+$string['revokethreshold_help'] = 'Login failures limit causing revoke of the generated password (0 - unlimited).';
+$string['minrequestperiod'] = 'Minium period';
+$string['minrequestperiod_help'] = 'A time in seconds after which another password can be generated.';
 $string['fieldsmapping'] = 'User profile fields mapping';
 $string['fieldsmapping_pattern'] = 'Pattern';
 $string['fieldsmapping_pattern_help'] = 'Capturing groups PCRE patttern.';
diff --git a/lang/pl/auth_emailotp.php b/lang/pl/auth_emailotp.php
index 7f92af9..f1a8863 100644
--- a/lang/pl/auth_emailotp.php
+++ b/lang/pl/auth_emailotp.php
@@ -27,7 +27,13 @@ $string['otpgeneratedsubj'] = 'Hasło jednorazowe';
 $string['otpgeneratedtext'] = 'Hasło jednorazowe dla bieżącej sesji: {$a->password}';
 $string['otpsentsuccess'] = 'Hasło jednorazowe zostało wysłane na podany adres email.';
 $string['otpsenterror'] = 'Wystąpił błąd podczas wysyłania hasła jednorazowego.';
-$string['otpsentinfo'] = 'Hasło jednorazowe dla bieżącej sesji już zostało wygenerowane i wyłane.';
+$string['otpsentinfo'] = 'Hasło jednorazowe dla bieżącej sesji już zostało wygenerowane i wysłane.';
+$string['otpinvalidated'] = 'Poprzednio wygenerowane hasło zostało unieważnione z powodu przekroczenia limitu niepoprawnych logowań.';
+$string['optperioderror'] = 'Nie zachowany minimalny odstęp, po którym kolejne hasło może być wygenerowane. Spróbuj ponownie później.';
+$string['revokethreshold'] = 'Próg nieważnienia';
+$string['revokethreshold_help'] = 'Limit nieudanych logowań unieważniających wygenerowane hasło (0 - bez limitu).';
+$string['minrequestperiod'] = 'Minimalny odstęp';
+$string['minrequestperiod_help'] = 'Czas w sekundach, po którym kolejne hasło może być wygenerowane.';
 $string['fieldsmapping'] = 'Mapowanie pól profilu użytkownika';
 $string['fieldsmapping_pattern'] = 'Wzorzec';
 $string['fieldsmapping_pattern_help'] = 'Grupujące wyrażenie regularne PCRE.';
diff --git a/settings.php b/settings.php
index 9a9dc22..1a10d61 100644
--- a/settings.php
+++ b/settings.php
@@ -52,6 +52,17 @@ if ($ADMIN->fulltree) {
         get_string('fieldsmapping_mapping', 'auth_emailotp'),
         get_string('fieldsmapping_mapping_help', 'auth_emailotp'), '', PARAM_RAW_TRIMMED));
 
+   $settings->add(new admin_setting_heading('auth_emailotp/security',
+        new lang_string('security', 'admin'), '')); 
+
+    $settings->add(new admin_setting_configtext('auth_emailotp/revokethreshold',
+        get_string('revokethreshold', 'auth_emailotp'),
+        get_string('revokethreshold_help', 'auth_emailotp'), 3, PARAM_INT));
+
+    $settings->add(new admin_setting_configtext('auth_emailotp/minrequestperiod',
+        get_string('minrequestperiod', 'auth_emailotp'),
+        get_string('minrequestperiod_help', 'auth_emailotp'), 120, PARAM_INT));
+
     // Display locking / mapping of profile fields.
     $authplugin = get_auth_plugin('emailotp');
     display_auth_lock_options($settings, $authplugin->authtype, $authplugin->userfields,