W32/Sdbot-YK is a worm which attempts to spread to remote network shares. It also contains backdoor Trojan functionality, allowing unauthorised remote access to the infected computer via IRC channels.
W32/Sdbot-YK spreads to network shares as a result of the backdoor element receiving the appropriate command from a remote user.
W32/Sdbot-YK moves itself to the Windows system folder as winxtn.exe and creates the following entries in the registry so as to run itself on system startup:
HKCU\Software\Microsoft\Windows\CurrentVersion\RunServices
XTN Service Drivers
winxtn.exe
HKCU\Software\Microsoft\Windows\CurrentVersion\Run
XTN Service Drivers
winxtn.exe
HKLM\Software\Microsoft\Windows\CurrentVersion\RunServices
XTN Service Drivers
winxtn.exe
HKLM\Software\Microsoft\Windows\CurrentVersion\Run
XTN Service Drivers
winxtn.exe
W32/Sdbot-YK may also set the following registry entries:
HKLM\SYSTEM\CurrentControlSet\Control\Lsa
XTN Service Drivers
winxtn.exe
HKLM\SOFTWARE\Microsoft\Ole
XTN Service Drivers
winxtn.exe
W32/Sdbot-YK also drops Troj/NtRootk-F as msdirectx.sys and installs it as a service with the name "msdirectx".