Transfer box leak

I was crawling around / under / over the car with the camera the other day, & thought I'd take pics of issues as I found em.

Think I might have a leak from the transfer box drain plug. Do these plugs often leak, and is there a washer or seal with it?

Here's a pic - what do you think?

no seal or washer works on a taper.the 2 lower sump plate nuts often leak can be slackened and siliconed as can plug

Thanks, I'll clean it up, then take another look to try and work out which it is.

It was the sump plate nut. Will any silicone do, or is there an automotive one that's more oil / heat resistant.

you can get automotive rtv silicone but any would do