I have had someone access my account, play a few games, changed my settings and spend some in game currency. I've changed my password, buy how else can I prevent this from happening? How were they able to in the first place?

I bottom frag in dm too much and it pisses me off. How do I get more kills in dm? Idk how these guys are so good at clicking heads, like I don’t even get a chance to shoot my gun. These guys in dm just on crack. Very tilting experience.