The company that hosts my server has been getting e-mails from other people telling them they are receiving break in attemps from my transit IP.

Below is one of the e-mails the company that hosts my server received:

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Our company is receiving break-in attempts from IP (my transit IP Number). It has lasted over two days now and shows no sign of stopping. Example: Jan 12 06:53:58 6E:server sshd[45425]: Illegal user admin from (my transit IP Number) Please take a look when you get a chance. The IP traced back to your domain.
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Can anyone tell me how to go about checking this out, or how I get to my log files on Plesk 7.5? I want to get this problem straightened out asap.

Thank you!

Jaime