Wireless Router Security

So, as for that post I said that was a post all its own on the ISP bandwidth being maxed out - I have a wireless router, and after my mom died my sister was coming over here a lot and needed to work, so I set up the router to be unsecured so she could use the Internet from here.

That was no problem, until I got an e-mail from my ISP that I was almost maxed out on my allowed 10 GB of bandwidth.

Now, over the past year my usage has been....

2.99 GB in October '07
4.81 GB in November '07
3.75 GB in December '07
2.81 GB in January '08
2.34 GB in February '08
1.96 GB in March '08
2.23 GB in April '08
5.23 GB in May '08
5.61 GB in June '08
2.53 GB in July '08
3.12 GB in August '08
4.23 GB in September '08
3.96 GB in October '08
9.41 GB used so far for November '08

That is an average use of 3.50 GB a month for just over a year. In May and June I caught up on watching Heroes and watched a few movies on Netflix online. I unlocked my wireless router for my sister in September, and that was the month that I spent a lot of time watching movies and television shows online (caught up on past episodes of Prison Break). So, for my average use to nearly triple in a month when my sister has not been using my wireless access, and when I have only watched one episode of a TV program online ... there's gotta be someone else piggybacking off my access. I've turned the security lock back on.