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Improved detection and protection against business email compromise (BEC) such as CEO fraud #1269

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Improved detection and protection against business email compromise (BEC) such as CEO fraud #1269

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98 changes: 97 additions & 1 deletion modules/imap/handler_modules.php
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Original file line number Diff line number Diff line change
Expand Up @@ -854,7 +854,21 @@ public function process() {
$msg['server_id'] = $form['imap_server_id'];
$msg['server_name'] = $details['name'];
$msg['folder'] = $form['folder'];
$msgs[] = $msg;
$uid = $msg['uid'];
$part = true;
$max = 87;
$msg_struct = $imap->get_message_structure($uid);
$struct = $imap->search_bodystructure($msg_struct, array('imap_part_number' => $part));
$msg_struct_current = array_shift($struct);
$msg_text = $imap->get_message_content($uid, $part, $max, $msg_struct_current);
// remove line 858 to 863 when https://github.com/cypht-org/cypht/pull/1241 is merged

$isValid = $this->validationMessage($msg['to'], $msg['subject'], $msg_text, $imap, $this->cache, $form['imap_server_id']);
if ($isValid) {
$msgs[] = $msg;
} else {
$msgs = [];
}
}
if ($imap->selected_mailbox) {
$imap->selected_mailbox['detail']['exists'] = $total;
Expand All @@ -868,6 +882,72 @@ public function process() {
$this->out('do_not_flag_as_read_on_open', $this->user_config->get('unread_on_open_setting', false));
}
}
public function validationMessage($email, $subject, $msg, $imap, $cache, $imap_server_id) {
// 1. Check Suspicious Terms or Requests
$suspiciousTerms = explode(",", $this->user_config->get("ceo_suspicious_terms_setting"));
if ($this->detectSuspiciousTerms($msg, $suspiciousTerms) || $this->detectSuspiciousTerms($subject, $suspiciousTerms)) {
// 2. check ceo_rate_limit
$amount = $this->extractAmountFromEmail($msg);
$amountLimit = $this->user_config->get("ceo_rate_limit_setting");
if ($amount > $amountLimit) {
// 3. Check Sender's Email Address
$folder = "Suspicious emails";
if (!count($imap->get_mailbox_status($folder))) {
$imap->create_mailbox($folder);
}
$server_id = $imap_server_id ."_". bin2hex($folder);

if ($this->user_config->get("ceo_use_trusted_contact_setting")) {
$contacts = $this->get('contact_store');
$contact_list = $contacts->getAll();
$existingEmails = array_map(function($c){
return $c->value('email_address');
},$contact_list);
if (!$this->isValidateAddrEmail(array_values($existingEmails), $email)) {
// 4. action to execute implement here
imap_move_same_server($server_id, "move", $cache, $folder);
}
} else {
// 4. action to execute implement here
imap_move_same_server($server_id, "move", $cache, $folder);
}
return false;
}
return true;
}
}
private function detectSuspiciousTerms($msg, $suspiciousTerms) {
foreach ($suspiciousTerms as $phrase) {
if (stripos($msg, $phrase) !== false) {
return true;
}
}

return false;
}
private function detectUnusualAmount($normalLimit, $amount) {
if ($amount > $normalLimit) {
return true;
}
return false;
}
private function isValidateAddrEmail($trustedDomain, $email) {
foreach ($trustedDomain as $e) {
if ($email === $e) {
return true;
}
}
return false;
}
private function extractAmountFromEmail($emailBody) {
$pattern = '/\b\d+(?:,\d+)?\.?\d*\s*(?:USD|dollars?|US\$?|EUR|euros?|€|JPY|yen|¥|GBP|pounds?|£|CAD|CAD\$|AUD|AUD\$)/i';

preg_match_all($pattern, $emailBody, $matches);

if (count($matches[0]) > 0) {
return $matches[0][0];
}
}
}

/**
Expand Down Expand Up @@ -2194,3 +2274,19 @@ function process_move_messages_in_screen_email_enabled_callback($val) { return $
process_site_setting('move_messages_in_screen_email', $this, 'process_move_messages_in_screen_email_enabled_callback', true, true);
}
}

/**
* Process setting_ceo_detection_fraud in the settings page
* @subpackage core/handler
*/
class Hm_Handler_process_setting_ceo_detection_fraud extends Hm_Handler_Module {
public function process() {
function process_ceo_use_trusted_contact_callback($val) { return $val; }
function process_ceo_suspicious_terms_callback($val) { return $val; }
function process_ceo_rate_limit_callback($val) { return $val; }

process_site_setting('ceo_use_trusted_contact', $this, 'process_ceo_use_trusted_contact_callback');
process_site_setting('ceo_suspicious_terms', $this, 'process_ceo_suspicious_terms_callback');
process_site_setting('ceo_rate_limit', $this, 'process_ceo_rate_limit_callback');
}
}
37 changes: 37 additions & 0 deletions modules/imap/output_modules.php
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Original file line number Diff line number Diff line change
Expand Up @@ -1470,3 +1470,40 @@ protected function output() {
return $res;
}
}
class Hm_Output_setting_ceo_detection_fraud extends Hm_Output_Module {
protected function output() {
$settings = $this->get('user_settings', array());
$ceo_use_trusted_contact = "checked";
$ceo_suspicious_terms = "wire transfer, urgent, account details, payment instruction";
$ceo_rate_limit = "100";
if (array_key_exists('ceo_use_trusted_contact', $settings)) {
if ($settings['ceo_use_trusted_contact']) {
$ceo_use_trusted_contact = "checked";
} else {
$ceo_use_trusted_contact = "";
}
}

if (array_key_exists('ceo_suspicious_terms', $settings) && $settings['ceo_suspicious_terms']) {
if ($settings['ceo_suspicious_terms']) {
$ceo_suspicious_terms = $settings['ceo_suspicious_terms'];
}
}
if (array_key_exists('ceo_rate_limit', $settings) && $settings['ceo_rate_limit']) {
if ($settings['ceo_rate_limit']) {
$ceo_rate_limit = $settings['ceo_rate_limit'];
}
}

$res = '<tr class="general_setting"><td><label for="ceo_use_trusted_contact">'.
$this->trans('CEO fraud: Use Trusted Contacts as Valid emails').
'</label></td><td><input class="form-check-input" type="checkbox" role="switch" id="ceo_use_trusted_contact" name="ceo_use_trusted_contact" '. $ceo_use_trusted_contact .' ></td></tr>';
$res .= '<tr class="general_setting"><td><label for="ceo_suspicious_terms">'.
$this->trans('CEO fraud: Suspicious Phrases or Requests(separate by ",")').
'</label></td><td><textarea class="form-control form-control-sm w-auto" role="switch" id="ceo_suspicious_terms" name="ceo_suspicious_terms">'. $ceo_suspicious_terms .'</textarea></td></tr>';
$res .= '<tr class="general_setting"><td><label for="ceo_rate_limit">'.
$this->trans('CEO fraud: Rate-Limit or Monitor Unusual Requests').
'</label></td><td><input class="form-control form-control-sm w-auto" type="number" min="0" role="switch" id="ceo_rate_limit" name="ceo_rate_limit" value="'. $ceo_rate_limit .'" ></td></tr>';
return $res;
}
}
5 changes: 5 additions & 0 deletions modules/imap/setup.php
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Original file line number Diff line number Diff line change
Expand Up @@ -45,6 +45,7 @@
add_handler('settings', 'process_auto_advance_email_setting', true, 'imap', 'date', 'after');
add_handler('settings', 'process_first_time_screen_emails_per_page_setting', true, 'imap', 'date', 'after');
add_handler('settings', 'process_setting_move_messages_in_screen_email', true, 'imap', 'process_first_time_screen_emails_per_page_setting', 'after');
add_handler('settings', 'process_setting_ceo_detection_fraud', true, 'imap', 'process_setting_move_messages_in_screen_email', 'after');
add_output('settings', 'imap_server_ids', true, 'imap', 'page_js', 'before');
add_output('settings', 'start_sent_settings', true, 'imap', 'end_settings_form', 'before');
add_output('settings', 'sent_since_setting', true, 'imap', 'start_sent_settings', 'after');
Expand All @@ -62,6 +63,7 @@
add_output('settings', 'imap_auto_advance_email', true, 'imap', 'imap_pagination_links', 'after');
add_output('settings', 'first_time_screen_emails_per_page_setting', true, 'imap', 'imap_auto_advance_email', 'after');
add_output('settings', 'setting_move_messages_in_screen_email', true, 'imap', 'first_time_screen_emails_per_page_setting', 'after');
add_output('settings', 'setting_ceo_detection_fraud', true, 'imap', 'default_sort_order_setting', 'after');

/* compose page data */
add_output('compose', 'imap_server_ids', true, 'imap', 'page_js', 'before');
Expand Down Expand Up @@ -438,5 +440,8 @@
'tag_id' => FILTER_DEFAULT,
'first_time_screen_emails' => FILTER_VALIDATE_INT,
'move_messages_in_screen_email' => FILTER_VALIDATE_BOOLEAN,
'ceo_use_trusted_contact' => FILTER_VALIDATE_BOOLEAN,
'ceo_suspicious_terms' => FILTER_DEFAULT,
'ceo_rate_limit' => FILTER_VALIDATE_INT,
)
);