Putty is a very popular open source SSH/Telnet client which can be used to connect to other devices and machines, such as Linux plus also some firewalls and other networking devices. It runs on Windows and has an installed version plus also a portable client.
Some hackers have decided to exploit this by adding code which uploads the credential information to a 3rd party server.
There’s no mention in the code to suggest the uses of this stored information, but obviously it will not be used for legal uses.
Unfortunately this is very easy to do with open source projects, the hard thing is to get critical exposure. The difference here is that the hackers used a variety of SEO techniques to get the sites hosting the compromised version up the search engine listings.
This has been done before with FileZilla. The compromised software being nicknamed Stealzilla.
Further information plus how to identify if you are running a compromised version below: