SAN FRANCISCO (Reuters) - Security experts warned on Monday about a new virus outbreak that was spreading quickly across the Internet.
The new virus, dubbed MyDoom or Novarg, is a mass-mailing worm that arrives as an attachment with an .exe, .scr, .zip or .pif extension and can have a subject line of "test" or "status."

It mails itself out to addresses in the victim's computer and is clogging mail servers and degrading network performance at companies, experts said.

"Mailboxes at large corporations are infected and reporting multiple infections throughout their entire organizations," said David Perry, global education director at Trend Micro.

The worm was discovered on Monday afternoon and spread so quickly that Trend Micro, Network Associates, Symantec and other anti-virus companies were rating it a "high" outbreak.

Security experts said they were still analyzing the virus to discover what it does to the victim computers.