Troj/Ist-B is a keylogging Trojan.
When run, Troj/Ist-B copies itself to the Windows System folder as ist2.exe and creates the following registry entry in order to run itself on system startup:
HKLM\Software\Microsoft\Windows\CurrentVersion\Run\
Version Information = C:\WINDOWS\system\ist2.exe
The Trojan runs in the background and logs all keypresses to a file WINDOWSKJ.LOG in the Windows System folder.