Badtrans worm leaves back doors, logs data

IDG News Service - A new variant of a mass-mailer Internet worm that installs a backdoor program that can allow attackers to access recipients' computers was spreading on the Internet today, according to virus alerts from several antivirus companies.

The worm, called Badtrans.b, is a new variant of the older Badtrans virus, according to the companies. The variant is executed when a user opens an infected e-mail; it doesn't require a user to click on an attachment, as many mass-mailer worms do, according to virus alerts from Germany-based Activis Ltd. and Reston, Va.-based TruSecure Corp. The worm exploits a security vulnerability in Microsoft Corp.'s Outlook and Outlook Express e-mail clients to automatically execute the attachment when the e-mail is opened, they said.

Badtrans is more devious in that it arrives in the recipient's in-box with "Re:" in the subject line to an e-mail actually sent by the user, according to Sunnyvale, Calif.-based McAfee.com Corp. and TruSecure. The worm is rated a medium risk.

There is some disagreement, however, as to what happens after the worm is executed. According to TruSecure and Santa Clara, Calif.-based Network Associates Inc., the parent company of McAfee.com, the worm will send itself to all e-mail addresses listed in unread messages in the victim system's in-box. Activis, however, contends that the worm sends itself to all addresses listed in the user's address book, much like other mass mailers.

What happens next isn't in doubt, however, as all companies agree that the worm then installs a Trojan horse, or backdoor, program that will allow an attacker to gain access to the infected computer and then attempts to send the IP address of the infected machine to the worm's author.

After execution, Badtrans also runs a keylogger program that can record all data entered via the keyboard, including passwords, credit card numbers and other personal information, according to Activis and McAfee.com. The data gathered by the keylogger is saved in encrypted form on the system's hard drive, they said.

The worm will appear in e-mail boxes with either no text in the body of the message or some of the original message's text, the companies said. The attachments included with the worm will appear to be .mp3, .doc or .zip files but are actually double-extension files with .scr or .pif extensions, the companies said. These attachments are 13,312 bytes in length, according to Network Associates.

The software vendors recommended that users update their antivirus software immediately and that companies block the transfer of attached files at their e-mail gateways. Users are alsourged to apply the patch to close the security hole that the worm exploits.