If your website is still running on legacy php version, you may consider to upgrade PHP version and your website’s source code to protect your website from future malware / malicious attack. The newer PHP version, the faster the performance, the more secure, and more efficient.

PHP 4: no longer supported by PHP Community
1&1 Extended Support available
PHP 5.2: no longer supported by PHP Community
1&1 Extended Support available
PHP 5.4: no longer supported by PHP Community
1&1 Extended Support available
PHP 5.5: no longer supported by PHP Community (since July 21st)
1&1 Extended Support available
PHP 5.6: support expected to end on Dezember 31, 2018
PHP 7: support expected to end on Dezember 03, 2018