Kaspersky (an antivirus vendor) have a stand-alone detection tool, available from their site See: http://support.kaspersky.com/viruses/utility - Flashfake removal tool; Further information about the tool is available from their news section: http://www.kaspersky.co.uk/news?id=207576489
You should disable all browser plugins that are a specific risk. However, because these versions will remain unpatched, the entrire rest of the operating system is still a risk. It would be advisable to switch to Debian PPC, to continue using this hardware with a supported operating system.
It is highly advisable that an antivirus product is installed on your Mac. Sophos Home Edition for Mac is available for both Intel and PPC Macs: http://www.sophos.com/en-us/products/free-tools/sophos-antivirus-for-mac-home-edition.aspx