I see that someone is trying to login as 'sa' on our MS SQL server. Besides changing the port to something other then 1433 and separating the SQL server, is there anything else I can do to lower the amount of attacks?

I don't know what happened to you but I know that Plesk creates the 'SA' user for the built in MSDE that it has.

Cheers,

Don't make it accessible to the outside world.

Two ways:

change the SQL Server port - very easy, just edit WindowsSystem32driversetcservices and modify the two ms-sql-s entries to new ports

or

install a firewall - Routing and Remote Access is just fine.

Yes, I had that trouble - SA is the SQL Admin account that is built in to SQL Server, and SQL Server, by default, listens on port 1433, so is an easy target for bots and crap like that. You can't turn it off, so either change it or block it. A secure password is probably good enough to avoid a brute force hack, but it's still using resources on your server

As Kyle suggested

If you have (MS [Sql Server Client Network Utility] ) then just disable tcp/Ip and alter a few other options that suit your needs.
That should help fix it unless you require your clients to connect to SQL from a remote location.

If you have limited experience using MSSQL use (MS [Enterprise Manager Utility]) then you should have no problem changing the default sa account name on your SQL server.

Check out this site for further instructions
to help aid and track/Fix most errors produced
by the SQL service or errors produced by the system. http://www.eventid.net