At the University of Hawai'i, the volume of e-mail disrupted some communications, and at healthcare insurer HMSA the virus temporarily shut down incoming and outgoing e-mail yesterday and again this morning.

"The volume of e-mail disrupted mail service both in terms of performance of our e-mail servers and the ability of people to use their e-mail, because of the junk in there relative to actual messages," said David Lassner, UH chief information officer. "But we’re hopefully on the way back to normal service."

At HMSA, claims processing continued as normal and e-mail service resumed after periodic suspensions, said spokesman Chuck Marshall.

Meanwhile, Hawai'i Pacific University officials applied lessons learned from past virus attacks, such as the attack by last year’s Sobig, which shut down e-mail as well as the university’s computer network. The steps taken included monitoring security Web sites and keeping operating system and anti-virus software updated, said Justin Itoh, HPU chief information officer.

"The users don’t see any difference at all, which is a big change from the other one," he said. "This time we already knew about it Monday of last week, so we were well ahead of the game."

Unlike other mass-mailing worms, Mydoom does not attempt to trick victims by promising nude pictures of celebrities or mimicking personal notes. Instead, one of its messages reads: "The message contains Unicode characters and has been sent as a binary attachment."

When launched on computers running Microsoft Corp.’s Windows operating systems, the attached file can send out 100 infected e-mail messages in 30 seconds to e-mail addresses stored in the computer’s address book and other documents.

Besides sending out tainted e-mail, the program appears to open up a backdoor so hackers can take over the computer later.

Microsoft offers a patch of its Outlook e-mail software to warn users before they open such attachments or prevent them from opening them altogether. Anti-virus software also stops infection.