Question Hacked forum posts

Supplement:
It seems, you have a second account as user andrewn1951. With this account you've subscribed the category: General questions and how-tos (Alias: general-questions-and-how-tos).

These have been going on for some months though only between 4 and 10 per day. I would imagine that somebody has automatic login enabled which allows the postings. I have been though these types of situations else where. Sometimes they come from throwaway email IP ranges so you block those. I also used the web spam systems that is also included in Kunena and other extensions that works like a look up. But I would imagine with this small amount it is coming from one subscribers account and if that account is tracked you can have a word with them as it is likely that their system is compromised. I have even threatened to block people if they do not sort out their issue. I used to work in a secondary school responsible for the running of the whole network, computers, servers, software and security of the system. That was a nightmare with access from almost a thousand students plus staff all having access and all using portable drives and flash drives. However sometimes you just have to accept that you cannot stop them all. What surprises me is the number of so called IT, Internet and website creators that don't take real precautions to prevent their systems being compromised.

If you use Kunena, you do not need to allow subscriptions. Then no mails will be sent to users. But the problem of the topic starter is another.
Nothing has been hacked here. The user receives only the mails of categories, which he has subscribed to. He can unsubscribe this categories at any time.