Loaded Commerce Community

Just today we started receiving orders for < $ .99. No orders are being logged in our CRELoaded admin but Authorize.net is recording the orders.

IP address of 213.175.218.178 is accessing /ssl_merch.php in our store to process these transactions.

It's apparent that whomever is doing this is trying to determine which credit cards he/she has are valid. Outside of blocking the users IP address, is there anything else I can do to prevent this from happening? I searched the boards and did not find anything related to this.

Thanks in advance for your help/advice/suggestions!

Edit:

The only entries in our log files originating from this IP are:

213.175.218.178 - - [21/Jul/2011:XX:12:XX -0400] "POST /ssl_merch.php HTTP/1.1" 200 207 "-" "-"

Apart from - 1) don't use authorize.net 2) upgrade to 6.4.x ?

Simon

where does somebody go to pay for someone to assess and address matters regarding security?

Your hosting company (hopefully.)
I need to put my sig in block capitals it seems.

Simon