TANs (Transaction Number) can only be used for personal transactions. Your bank will never ask you to enter a TAN for prize draws, security updates or to refund money to your account. Hence, please always use caution if you are asked for your bank details or a TAN when you are not actually making a transaction.
E-mails and attachments can contain viruses and Trojans and infect your computer and smartphone. For this reason, do not open attachments of unknown origin, treat e-mails with promises in their subject line with caution and delete all e-mails sent by unknown senders.