Hackers have not even spared the new and refreshing Google+. It has become the new underground for hackers. Hackers have targeted Google Plus, the new social networking service by Google. The scam is all about the fake invites being sent to all people wanting to be a part of Google+.
The fake invites that are part of these scams are spreading through emails. These fake invites look extremely similar to the actual invites and hence they are easily trapping people. Even the e-mail addresses given at the bottom look as if the mail was coming from a Google+ member. Google plus invites and Google Plus invitations had become very searched on the internet and so probably the hackers targeted Google Plus as well.
Also, if you at all click on a link in the message (which is not recommended) a website trying to sell you penis enlargement products would appear. To avoid any such nuisance, avoid clicking on suspicious links for want of invites. Be careful while accepting an invite an make sure that it is coming from a trusted source.