fortunately, on my wag160n it doesn't seem exposed to the internet

That's not to say somebody can't embed something on a web page (E.G. flash) that connects to 192.168.1.1 and enables configuration from WAN :)

Flash won't let you open connections to other hosts (unless there's a crossdomain.xml file that allows it).

With html/javascript you can send http requests to other hosts, but you can't read the response. It seems like the backdoor isn't accessed over http, so that wouldn't help you either.