Who is doing this and Why?

ourdomain.com /? add %spam%words%related%to %our %enemies

[bigjohnt]

I just noticed this on a major client's SERPs at google.... literally dozens of pages apparently submitted with character strings after the /? that are totally absolutely not our terms
Of course the links go to their main site.

Can they be penalized, and any ideas where this comes from?

[bigjohnt]

nevermind. found it. total spamfest using google's api and cache. he will suffer.
g'day.