  This article discusses the security of McEliece-like encryption schemes using
subspace subcodes of Reed-Solomon codes, i.e. subcodes of Reed-Solomon codes
over $\mathbb{F}_{q^m}$ whose entries lie in a fixed collection of
$\mathbb{F}_q$-subspaces of $\mathbb{F}_{q^m}$. These codes appear to be a
natural generalisation of Goppa and alternant codes and provide a broader
flexibility in designing code based encryption schemes. For the security
analysis, we introduce a new operation on codes called the twisted product
which yields a polynomial time distinguisher on such subspace subcodes as soon
as the chosen $\mathbb{F}_q$-subspaces have dimension larger than $m/2$. From
this distinguisher, we build an efficient attack which in particular breaks
some parameters of a recent proposal due to Khathuria, Rosenthal and Weger.
