  We present preliminary results for strangeness form factors of the nucleon
computed on the CLS ensembles with $N_f=2+1$ flavors of O($a$)-improved Wilson
fermions. Our calculations are performed at two values of the lattice spacing
($a \in \{0.064, 0.086\} \,\mathrm{fm}$) and three values of the pion mass
($m_\pi \in \{ 200, 280, 340\} \,\mathrm{MeV}$). The determination of
strangeness form factors proceeds by computing quark-disconnected diagrams, for
which we employ hierarchical probing in four dimensions in order to deal with
this most challenging part of the calculation. Furthermore, we investigate
several source-sink separations to check for excited-state contamination.
