A new computer virus that attacks the computer password, manipulates and eventually blocks the user to log in to the computer is spreading, Yonhap reported Saturday.

The virus, an advanced form of ``Win32.HLLW.Shadow.based'' that showed up last month, locks up the computer, resulting in log in error. It also paralyzes the network by overloading the traffic on the 445 port.

A free vaccine is available on the Web site of the anti-virus company, New Technology Wave (www.viruschaser.com).

The vaccine provider also advises computer users to regularly change their computer passwords and update Windows security patches. Once infected, the virus detours the radar of the previously installed vaccine program on the computer and makes it undeletable, the company said.