see security warning by the author Simon Tatham
http://lists.tartarus.org/pipermail/putty-announce/2013/000018.html
"All the pre-built binaries, and the source code, are now available
from the PuTTY website at
http://www.chiark.greenend.org.uk/~sgtatham/putty/
<http://www.chiark.greenend.org.uk/%7Esgtatham/putty/>
This is a SECURITY UPDATE. We recommend that _everybody_ upgrade, as
soon as possible.
This release fixes multiple security holes in previous versions of
PuTTY, which can allow an SSH-2 server to make PuTTY overrun or
underrun buffers and crash...."