Is there an attack signature for OpenVAS ?

Go to Security ›› Options : Application Security : Attack Signatures : Attack Signature List.

There is no Attack Signature for OpenVAS scanner - I just checked the latest ASM Signature update dated 2019-04-17 11:29:45.

It isn't difficult to create a user-defined signature as OpenVAS has a User-Agent string like this:

"Mozilla/5.0 [en] (X11, U; OpenVAS 7.0.10)"
"Mozilla/5.0 [en] (X11, U; OpenVAS 8.0.9)"

so by creating a user-defined signature looking for "OpenVAS" in the header should work. It should look like this:

headercontent:"OpenVAS";

Ideally however it is best to raise a Support Case with F5 as OpenVAS scanner signature is missing and needs to be a part of standard signatures