If you're one of the unlucky users who has had their Xbox Live account targeted by a spam bot, rest assured that Microsoft is aware of it. Apparently, the spammers aren't simply hard at work annoying people on Xbox Live, it's being said to be occurring on PlayStation and Skype as well.
According to the Xbox sub-Reddit mods, Microsoft is "well aware" of the spam issue and are "working day and night to fight against it." While Microsoft is battling the spam bots, it's being advised that you do not follow any links sent to you by a spam bot or someone you do not know.
In addition to that, it's being suggested that you report the message to Microsoft, not the account, and block the user. Reporting messages makes it easier for enforcement to take action.