MountainC

It seems that this Trojan deserted my IIS log files. The logs in event viewer shows like this: Object name: C:\inetpub\logs\LogFiles\W3SVC2\u_ex230210.log//data0016. Object type: N/A. Danger level: high. Certainty level: partial signature match. Detected object type: Trojan. Detected: HEUR:Exploit.Multi.Desert.gen. Task name: KS10.1 - On-Demand Scan. User name: SYSTEM. Computer name: localhost. Process: N/A. PID: 0. How can I resolve this problem? And what causes this?