No, PureCloud does not collect the IP address of the user initiating the chat. You could add this in the custom data so it's available in participant attributes if you need it.
However, I would suggest building your anti-spam feature into your website without using PureCloud. PureCloud isn't built for that, and looking up IP addresses for each conversation before a chat is started will be functionally impossible for your use case. Because you can only make up to 300 requests per minute and would need to check thousands or millions of conversations for an IP address match, your use case is best suited for a database outside of PureCloud.