Is your machine open to the Internet? What protections do you load onto it? How is it firewalled? In short, what kind of access is available?
An unprotected machine facing the Interet can become infected in 15 minutes according to reports I have read. You need to provide protections to avoid tis from happening.
Firewall teh machine, opening only the ports needed for the type of machine it is intended to be. If FTP is to be offered, consider how to handle the write option carefully.
A good anti-virtus software also helps to protect the amchine.
If your machine does not have access to the Internet, but is on a network, you have bigger problems because the attacks are coming from within your own network. You’ll need ot root this stuff out of the network, even if it means checking wach machine inthe network. All network access for all machines should be blocked until the culprit machine or machines are found.