They are actually quite crafty. They use multiple servers, different email addresses, multiple user names and other tricks that make it difficult to defeat them with simple blocking. I have asked if we can put new members on hold until they are approved to eliminate the posts.
The last time I checked they were spamming for a gambling site in Korea. I would avoid it. Lately they have been submitting varied messages probably all to the same place but if I cant read it I don't take the chance. Just like you should never open emails or attachments from unknown senders.
There has been an increase in Ransom ware lately so it is always better to be safe.