Can I prevent somebody from joining a public group?

Question

Today some jerk joined the Arqade group on Steam and started spamming people with links to a lookalike phishing site. You know, like this but with "store.steampowered.com" instead of "twitter.com":

^{Image from the OpenDNS Phishing quiz. Hint: this one is a phish.}

Now, I've kicked him from the group and flagged his account, but... it's a public group! Anybody can join. We'd rather not change that and still keep him out.

Is kicking sufficient? What else can I do?

Answer 1

You can't ban people from groups permanently, unfortunately.

What you can do is to report people via their profile and Steam will have a look at it.

You can also ban him from the groupchat.

Answer 2

Sadly, nothing stops him from joining again.

Is he spamming on community page/forums, Steam Group chat, or individual chat? For page, maybe there is some mute or some way to remove his permissions, but for chats, you can only block him.