Alarm that Internet Explorer could spread large-scale website infections has broken out, following the discovery of the first ever HTML (hyper text mark up language) virus.

The bug, which does not affect Netscape Navigator, Opera or other browsers except Explorer, attaches itself to any HTML files it finds. When these files are read by Explorer the virus is replicated into other HTML files, using Visual Basic to search the local system and modify its targets. The process repeats every time the browser looks at an infected file.

The Moscow lab which identified the bug compared it to the recent Windows scripting virus, 'Winscript.Rabbit', because it uses scripts rather than binary coding to work its mischief. While the bug has not caused any damage so far, anti-virus vendor Central Command, which was linked to the discovery, argued that the new type of virus will eventually become malicious.

The virus only affects Explorer because of its dependence on Visual Basic.