Installation to system
The worm's dropper installs the following files:
The file svchost.exe is the actual worm main file. SqlScan.exe is a port scan utilty and SqlExp.exe is a component that is used in MSDTC exploiting.
The worm may also create the following files:
These files are used in exploiting.
Spreading using MSTDC vulnerability
The worm scans for systems vulnerable to MSTDC (MS05-051) through TCP/1025. It constructs random addresses using a fixed list of A-class networks. If it finds a system responding to TCP SYN scan, it sends the exploit payload. The payload connects to remote address and waits for instructions. At the time of this writing, the server instructs the infected system to download and execute the worm's dropper and keylogger.
Please see the following page for detailed information on the vulnerability:
Dasher.B is detected with the following F-Secure Anti-Virus updates:
Version = 2005-12-15_05
Write-up: Jarkko Turkulainen
Technical Details: Jarkko Turkulainen, December 15, 2005
Description Updated: Jarkko Turkulainen, December 15, 2005