Almost 87,000 e-mails containing a new version of the Sober worm have been sent to UK businesses since one o'clock this morning, according to enterprise e-mail security company BlackSpider Technologies.
BlackSpider said the peak infection rate of the Sober.n worm was likely to rise as the UK business day got under way.
As of 8.30am today, barely any anti-virus supplier had issued a patch against the worm, according to BlackSpider.
The Sober.n virus carries a payload of 73K. There are two versions, one in English and the other in German.
The subject line of the English version is "I've_got your EMail on my_account!". The attachment in the e-mail is in zip format and both versions contain an executable file which shouldn’t be opened.
If it is, the worm is designed to infect users' machines and replicate itself by sending itself to other users, resulting in clogged up networks.
The body of the text in the e-mail, in broken English, reads as follows:
First, Very Sorry for my bad English.
Someone is sending your private e-mails on my address.
It's probably an e-mail provider error!
At time, I've got over 10 mails on my account, but the recipient are you.
I have copied all the mail text in the windows text-editor for you & zipped then.
Make sure, that this mails don't come in my mail-box again.