Hi Tim,
usually, this is pretty straight forward.
1) Get ClamAV to run on the same machine (note, that this is not a strict requirement) and then get it to listen on port 3310. This is not part of Membrane Service Proxy. Looking for instructions on how to get this up and running, I found
https://serverfault.com/a/798905 . That looks promising to me, although I have not tested it.
2) Simply put
<clamav />
into proxies.xml anywhere where an interceptor can go, e.g. after your
<validator/>.
That should be it.
Let us know if this doesn't work,
Tobias