|R u certain it is from Germany? Yes then track the address report it to microsoft.|
sometimes tho the person who attacks u is only being used him herself by someone else using the ip adress to spoof attack pc's.
Had it happen to me and the Chinese guy I tracked and abused was not pleased and offered the same explanation.
R Your firewall and anti virus are on real time protection and Scan daily shouldnt have any problems there are stacks of guards against ip attacks.