Problem behavior of this sort is sometimes observed in individuals with autism-spectrum disorders, but it sounds like this is new behavior from your brother. I'm not sure how old your brother is, but it sounds like he communicates effectively. The most successful interventions for this kind of behavior involve contingency management, and a behavior contract might be effective. It sounds like he understands that he shouldn't be doing this, given the fact that it sounds like he attempted to hide the fact that he was the one who did it. Getting mad at him isn't going to help, but explaining clearly that this sort of behavior is unacceptable, and arranging some contingencies for him is a good place to start. For example, something simple like grounding him from TV, video games, computer access (or other preferred activities) might be an effective consequence. In addition to that, you might add an additional incentive for going one week, two weeks, a month, etc... with no problem behavior like this. Explain the rules to him, be consistent about following through with them, and interventions like this are often effective.
This is not characteristic behavior of people with Asperger's Syndrome any more than it is characteristic behavior of "normal" people. I think your brother might have been misdiagnosed or might have some deeper psychological issues.