Have you read this thread? There is also another thread which apparently the user had posted a screenshot of a program which shows Chinese banner but I cannot find the thread.

It is unlikely that you can get your N900 infected with a virus. Though if you have been using sudo, gainroot, etc lots of times and you happen to execute files which just doesn't work then you maybe infected. The likelihood is quite rare to be frank, ARM virus which is specifically targeting maemo considering maemo is not really that popular.

Also with battery draining, there could be numerous issues such as overclocking, running too many programs, etc