Problem
This error message occurs:
SECURITY_VIOLATION
Solution
Usually, this is a temporary problem at the DHL webservice (API) and not an issue in the Magento extension.
However, if you see this error message in Magento 1 when using the Location Search feature (interactive map for DHL locations), it means that DHL has disabled the API "Location Search Europe" by now. The DHL Location Search feature in the Magento 1 checkout cannot be used anymore.