Guest Spam Postings and Session problem

Hi everyone.
Sine a while I have threats from guests in my board with spam content. Interesting is, that I do not allow guests to post.
Another problem I have is that the server load of the server where my site is on is very high in the last days. This information I got yesterday from my webhoster. He said that a defect database would cause a high server load.
I looked into the sessions and had oder 5000 entries. I deleted the entries and 24h later I had over 2000 entries again most of one specific session_ip. Another thing I recognised is the high number of SQL queries mostly over 80 (but only few members and guests are shown). The url of my board: http://www.das-bemalforum.de
Can anyone help me with this?
I have integra 1.40 with phpbb 2.0.19 running.
Greetings
Thorsten
Sine a while I have threats from guests in my board with spam content. Interesting is, that I do not allow guests to post.
Another problem I have is that the server load of the server where my site is on is very high in the last days. This information I got yesterday from my webhoster. He said that a defect database would cause a high server load.
I looked into the sessions and had oder 5000 entries. I deleted the entries and 24h later I had over 2000 entries again most of one specific session_ip. Another thing I recognised is the high number of SQL queries mostly over 80 (but only few members and guests are shown). The url of my board: http://www.das-bemalforum.de
Can anyone help me with this?
I have integra 1.40 with phpbb 2.0.19 running.
Greetings
Thorsten